fix: 修正学习流程中的证据、复习与进度问题

- 独立尝试按课程要求校验内容，不再任意输入即算独立成功
- 复习节点改为学后第 1/3/7/14 天，之后每 30 天抽查；复习轮换情境
- 掌握状态按作答记录推导：需认识、可回忆、跨情境使用及最近两次无帮助
- 课程证据按实际用到的目标记录；跟读与课程对话只算辅助练习
- 复习成功不再降低已有状态
- 学完课程后进入下一节未完成课程；全部学完后引导巩固与阶段评估
- 新增 3 题基础定位，按结果设置起始课程
- 新增按课程开放的对话场景，首页推荐最少练习的场景
- 切换课程时清空上一课的步骤进度
- AI 返回 JSON 格式并按 JSON 回放历史；拼写校验忽略大小写与连字符；移除学习目标选择

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

kouyu_english/lib/features/dialogue/dialogue_flow.dart

@@ -11,54 +11,93 @@ import '../../widgets/lexicon_lookup.dart';
 import '../../widgets/voice_answer.dart';
 
 class DialogueScenePage extends StatelessWidget {
-  const DialogueScenePage({super.key, required this.onStart, this.onBack});
-  final VoidCallback onStart;
+  const DialogueScenePage({
+    super.key,
+    required this.state,
+    required this.onStart,
+    this.onBack,
+  });
+  final AppState state;
+  final ValueChanged<String> onStart;
   final VoidCallback? onBack;
 
   @override
-  Widget build(BuildContext context) => AppPage(
-    appBar: onBack != null
-        ? AppBar(
-            leading: IconButton(
-              icon: const Icon(Icons.arrow_back),
-              tooltip: "返回",
-              onPressed: onBack,
-            ),
-            title: const Text("AI 情境对话"),
-          )
-        : null,
+  Widget build(BuildContext context) {
+    final recommended = state.recommendedScene;
+    return AppPage(
+      appBar: onBack != null
+          ? AppBar(
+              leading: IconButton(
+                icon: const Icon(Icons.arrow_back),
+                tooltip: "返回",
+                onPressed: onBack,
+              ),
+              title: const Text("AI 情境对话"),
+            )
+          : null,
+      child: SpacedColumn(
+        children: [
+          const Eyebrow('按当前水平推荐'),
+          Text(
+            '选一个场景，开口练习。',
+            style: Theme.of(context).textTheme.headlineMedium,
+          ),
+          Text(
+            '每轮 4 次回答，完成明确任务后结束。',
+            style: Theme.of(context).textTheme.bodyMedium,
+          ),
+          for (final scene in a0Scenes)
+            if (state.isSceneUnlocked(scene))
+              _OpenScene(
+                scene: scene,
+                recommended: scene.id == recommended.id,
+                onStart: () => onStart(scene.id),
+              )
+            else
+              _LockedScene(
+                title: scene.title,
+                note:
+                    'A0 · 学完第 ${lessonById(scene.unlockAfterLessonId!).number} 课后开放',
+              ),
+          const _LockedScene(title: '咖啡店点单', note: 'A1 · 后续版本开放'),
+        ],
+      ),
+    );
+  }
+}
+
+class _OpenScene extends StatelessWidget {
+  const _OpenScene({
+    required this.scene,
+    required this.recommended,
+    required this.onStart,
+  });
+  final DialogueScene scene;
+  final bool recommended;
+  final VoidCallback onStart;
+
+  @override
+  Widget build(BuildContext context) => SectionCard(
+    tint: recommended ? AppColors.softGreen : null,
     child: SpacedColumn(
       children: [
-        const Eyebrow('按当前水平推荐'),
-        Text('选一个场景，开口练习。', style: Theme.of(context).textTheme.headlineMedium),
-        Text(
-          '每轮 4 次回答，完成明确任务后结束。',
-          style: Theme.of(context).textTheme.bodyMedium,
+        Row(
+          mainAxisAlignment: MainAxisAlignment.spaceBetween,
+          children: [
+            Text(
+              scene.title,
+              style: const TextStyle(fontSize: 17, fontWeight: FontWeight.w600),
+            ),
+            Text(
+              recommended ? 'A0 · 推荐' : 'A0',
+              style: const TextStyle(color: AppColors.green),
+            ),
+          ],
         ),
-        SectionCard(
-          tint: AppColors.softGreen,
-          child: SpacedColumn(
-            children: [
-              const Row(
-                mainAxisAlignment: MainAxisAlignment.spaceBetween,
-                children: [
-                  Text(
-                    '初次见面',
-                    style: TextStyle(fontSize: 17, fontWeight: FontWeight.w600),
-                  ),
-                  Text('A0', style: TextStyle(color: AppColors.green)),
-                ],
-              ),
-              Text(
-                '介绍姓名、地点、状态或喜好，并反问对方',
-                style: Theme.of(context).textTheme.bodyMedium,
-              ),
-              PrimaryButton(label: '开始对话', onPressed: onStart),
-            ],
-          ),
-        ),
-        const _LockedScene(title: '认识新同学', note: 'A0 · 后续版本开放'),
-        const _LockedScene(title: '咖啡店', note: 'A1 · 后续版本开放'),
+        Text(scene.summary, style: Theme.of(context).textTheme.bodyMedium),
+        recommended
+            ? PrimaryButton(label: '开始对话', onPressed: onStart)
+            : SecondaryButton(label: '开始对话', onPressed: onStart),
       ],
     ),
   );
@@ -94,10 +133,14 @@ class DialoguePage extends StatefulWidget {
     required this.state,
     required this.onFinished,
     this.isLessonDialogue = false,
+    this.sceneId = 'a0-meet',
   });
   final AppState state;
   final ValueChanged<DialogueSummaryData?> onFinished;
   final bool isLessonDialogue;
+
+  /// The free scene to run when this is not a lesson dialogue.
+  final String sceneId;
   @override
   State<DialoguePage> createState() => _DialoguePageState();
 }
@@ -124,8 +167,18 @@ class _DialoguePageState extends State<DialoguePage>
   /// the dialogue ends: the spec forbids interrupting a beginner turn by turn.
   String? latestFeedback;
 
-  /// The free scene stores its draft under its own id.
-  static const _sceneDraftId = 'scene-a0-meet';
+  DialogueScene get _scene => sceneById(widget.sceneId);
+
+  /// A free scene may use everything the learner has finished so far.
+  String get _furthestCompletedLessonId => a0SeedLessons
+      .lastWhere(
+        (lesson) => widget.state.completedLessonIds.contains(lesson.id),
+        orElse: () => a0SeedLessons.first,
+      )
+      .id;
+
+  /// Each free scene stores its draft under its own id.
+  String get _sceneDraftId => 'scene-${_scene.id}';
 
   /// Closing line for the turn after the last scripted prompt. It stays inside
   /// taught A0 language instead of the old "Wonderful — nice meeting you!".
@@ -143,7 +196,7 @@ class _DialoguePageState extends State<DialoguePage>
               .id,
           widget.state.activeLessonId,
         )
-      : a0MeetDialogue;
+      : _scene.script;
 
   /// Only exact sentence matches are trusted. The old positional fallback
   /// attached `script.translations[stage]` to whatever the AI happened to say,
@@ -286,8 +339,10 @@ class _DialoguePageState extends State<DialoguePage>
       return;
     }
     widget.state.recordDialogueAttempt(
-      taskId:
-          'dialogue-${widget.isLessonDialogue ? _lessonSegmentId : 'a0-meet'}-$stage',
+      taskId: widget.isLessonDialogue
+          ? 'dialogue-$_lessonSegmentId-$stage'
+          : 'dialogue-scene-${_scene.id}-$stage',
+      sceneId: widget.isLessonDialogue ? null : _scene.id,
       rawAnswer: text,
       assisted: usedHelp,
       spoken: usedVoice && !transcriptEdited,
@@ -320,7 +375,10 @@ class _DialoguePageState extends State<DialoguePage>
           : 'nothing more, the conversation is finished',
       allowedLanguage: widget.isLessonDialogue
           ? taughtLanguageUpTo(widget.state.activeLessonId)
-          : allTaughtLanguage,
+          : _scene.unlockAfterLessonId == null
+          // The always-open scene mixes every A0 topic, as its script does.
+          ? allTaughtLanguage
+          : taughtLanguageUpTo(_furthestCompletedLessonId),
       history: turns
           .map(
             (turn) => <String, String>{
@@ -409,7 +467,7 @@ class _DialoguePageState extends State<DialoguePage>
     final personalSentence = learnerTurns.isEmpty
         ? 'My name is …'
         : learnerTurns.first.text;
-    widget.state.addDialogueRecap(personalSentence);
+    widget.state.addDialogueRecap(personalSentence, sceneId: _scene.id);
     widget.onFinished(
       DialogueSummaryData(
         // Only the turns the learner actually passed are reported.
@@ -584,7 +642,7 @@ class _DialoguePageState extends State<DialoguePage>
           onPressed: () => widget.onFinished(null),
         ),
         title: Text(
-          '${widget.isLessonDialogue ? '课程对话' : '初次见面'} · ${finished ? totalStages : stage + 1} / $totalStages',
+          '${widget.isLessonDialogue ? '课程对话' : _scene.title} · ${finished ? totalStages : stage + 1} / $totalStages',
         ),
       ),
       child: SpacedColumn(

kouyu_english/lib/features/home/home_page.dart

@@ -12,12 +12,16 @@ class HomePage extends StatelessWidget {
     required this.onStartPrimaryTask,
     required this.onOpenDialogue,
     required this.onResumeLessonDialogue,
+    required this.onStartReinforcement,
+    required this.onOpenAssessment,
   });
 
   final AppState state;
   final VoidCallback onStartPrimaryTask;
   final VoidCallback onOpenDialogue;
   final VoidCallback onResumeLessonDialogue;
+  final VoidCallback onStartReinforcement;
+  final ValueChanged<String> onOpenAssessment;
 
   @override
   Widget build(BuildContext context) {
@@ -26,16 +30,21 @@ class HomePage extends StatelessWidget {
     final activeLesson = lessonById(state.activeLessonId);
     final activeSegment = state.activeSegmentIndexFor(activeLesson.id) + 1;
     final resumeDialogue = state.hasResumableLessonDialogue;
+    final stageStep = !resumeDialogue && !isReview && state.allLessonsComplete
+        ? _stageStep()
+        : null;
     final primaryTitle = resumeDialogue
         ? '继续第 ${activeLesson.number} 课的课程对话'
         : isReview
         ? '先复习 $count 项'
-        : '第 ${activeLesson.number} 课 · ${activeLesson.title}${activeLesson.segments.length > 1 ? ' · 第 $activeSegment/${activeLesson.segments.length} 段' : ''}';
+        : stageStep?.title ??
+              '第 ${activeLesson.number} 课 · ${activeLesson.title}${activeLesson.segments.length > 1 ? ' · 第 $activeSegment/${activeLesson.segments.length} 段' : ''}';
     final primaryNote = resumeDialogue
         ? '已保留你的对话进度和提示状态。'
         : isReview
         ? (state.reviewBacklog ? '有积压项目；先花几分钟清掉到期复习。' : '昨天练过的关键句，今天换个情境再用一次。')
-        : '预热词汇 → 听说读写 → 对话 → 独立尝试';
+        : stageStep?.note ?? '预热词汇 → 听说读写 → 对话 → 独立尝试';
+    final scene = state.recommendedScene;
 
     return AppPage(
       child: SpacedColumn(
@@ -80,7 +89,9 @@ class HomePage extends StatelessWidget {
                       ),
                     ),
                     Text(
-                      isReview ? '${(count * 2).clamp(2, 10)} 分钟' : '12 分钟',
+                      isReview
+                          ? '${(count * 2).clamp(2, 10)} 分钟'
+                          : stageStep?.minutes ?? '12 分钟',
                       style: const TextStyle(color: AppColors.green),
                     ),
                   ],
@@ -94,10 +105,10 @@ class HomePage extends StatelessWidget {
                       ? '继续对话'
                       : isReview
                       ? '开始复习'
-                      : '开始今天的学习',
+                      : stageStep?.action ?? '开始今天的学习',
                   onPressed: resumeDialogue
                       ? onResumeLessonDialogue
-                      : onStartPrimaryTask,
+                      : stageStep?.onPressed ?? onStartPrimaryTask,
                 ),
               ],
             ),
@@ -110,7 +121,7 @@ class HomePage extends StatelessWidget {
                   style: TextStyle(fontSize: 16, fontWeight: FontWeight.w600),
                 ),
                 Text(
-                  '初次见面 · 4 个任务 · 文字或语音输入',
+                  '${scene.title} · ${scene.script.prompts.length} 个任务 · 文字或语音输入',
                   style: Theme.of(context).textTheme.bodyMedium,
                 ),
                 SecondaryButton(label: '开始情境对话', onPressed: onOpenDialogue),
@@ -122,6 +133,56 @@ class HomePage extends StatelessWidget {
       ),
     );
   }
+
+  /// What comes after the last A0 lesson: consolidation until the core items
+  /// are ready, then the stage assessment, then waiting for A1 content.
+  _StageStep _stageStep() {
+    final usable =
+        '可使用 ${state.coreUsableCount}/48 · 已掌握 ${state.coreMasteredCount}/30';
+    if (state.a0Passed) {
+      return _StageStep(
+        title: 'A0 已通过',
+        note: 'A1 课程准备中。先用巩固练习和情境对话保持手感。',
+        action: '安排一题巩固练习',
+        minutes: '3 分钟',
+        onPressed: onStartReinforcement,
+      );
+    }
+    final packId = state.nextAssessmentPackId;
+    if (state.a0AssessmentReady && packId != null) {
+      return _StageStep(
+        title: 'A0 阶段评估 · $packId',
+        note: '$usable。可以开始阶段评估，两套评估间隔至少 24 小时。',
+        action: '开始阶段评估',
+        minutes: '15 分钟',
+        onPressed: () => onOpenAssessment(packId),
+      );
+    }
+    return _StageStep(
+      title: state.a0AssessmentReady ? '第二套评估 24 小时后开放' : 'A0 课程已学完',
+      note: state.a0AssessmentReady
+          ? '第一套评估已通过。等待期间继续巩固。'
+          : '$usable。继续按时复习、做情境对话，达到要求后开放阶段评估。',
+      action: '安排一题巩固练习',
+      minutes: '3 分钟',
+      onPressed: onStartReinforcement,
+    );
+  }
+}
+
+class _StageStep {
+  const _StageStep({
+    required this.title,
+    required this.note,
+    required this.action,
+    required this.minutes,
+    required this.onPressed,
+  });
+  final String title;
+  final String note;
+  final String action;
+  final String minutes;
+  final VoidCallback onPressed;
 }
 
 class _FrameworkNote extends StatelessWidget {

kouyu_english/lib/features/lesson/lesson_flow.dart

@@ -38,6 +38,10 @@ class _LessonFlowState extends State<LessonFlow> {
   final writingController = TextEditingController();
   final independentController = TextEditingController();
   int selectedAnswer = -1;
+
+  /// Set once a wrong meaning is picked, so only a first-try choice counts as
+  /// recognition evidence.
+  bool listeningMissed = false;
   int previewIndex = 0;
   bool listeningAudioPlayed = false;
   bool showWritingHelp = true;
@@ -108,7 +112,12 @@ class _LessonFlowState extends State<LessonFlow> {
           correctAnswer: activity.answers.first,
           selectedAnswer: selectedAnswer,
           audioPlayed: listeningAudioPlayed,
-          onSelected: (value) => setState(() => selectedAnswer = value),
+          onSelected: (value) => setState(() {
+            selectedAnswer = value;
+            if (listeningOptions[value] != activity.answers.first) {
+              listeningMissed = true;
+            }
+          }),
           onPlayed: () => setState(() => listeningAudioPlayed = true),
           onLookup: () => showLexiconLookup(
             context,
@@ -118,7 +127,8 @@ class _LessonFlowState extends State<LessonFlow> {
           onContinue:
               selectedAnswer >= 0 &&
                   listeningOptions[selectedAnswer] == activity.answers.first
-              ? widget.state.completeListening
+              ? () =>
+                    widget.state.completeListening(recognized: !listeningMissed)
               : null,
         );
       case LessonStep.speaking:
@@ -126,7 +136,7 @@ class _LessonFlowState extends State<LessonFlow> {
           state: widget.state,
           text: activity.speaking,
           keepRecording: widget.state.keepRecordings,
-          onContinue: () => widget.state.completeSpeaking(assisted: true),
+          onContinue: widget.state.completeSpeaking,
         );
       case LessonStep.reading:
         content = _ReadingStep(

kouyu_english/lib/features/onboarding/onboarding_pages.dart

@@ -3,7 +3,11 @@ import 'package:flutter/material.dart';
 import '../../core/app_state.dart';
 import '../../core/app_theme.dart';
 import '../../core/models.dart';
+import '../../core/review_feedback.dart';
+import '../../core/seed_courses.dart';
+import '../../core/voice_service.dart';
 import '../../widgets/app_widgets.dart';
+import '../../widgets/voice_answer.dart';
 
 class WelcomePage extends StatefulWidget {
   const WelcomePage({super.key, required this.state, required this.onContinue});
@@ -16,13 +20,11 @@ class WelcomePage extends StatefulWidget {
 }
 
 class _WelcomePageState extends State<WelcomePage> {
-  late LearningGoal selectedGoal;
   late int selectedMinutes;
 
   @override
   void initState() {
     super.initState();
-    selectedGoal = widget.state.goal;
     selectedMinutes = widget.state.dailyMinutes;
   }
 
@@ -72,16 +74,6 @@ class _WelcomePageState extends State<WelcomePage> {
             style: Theme.of(context).textTheme.headlineMedium,
           ),
           const Text('从真实生活场景开始，先做到听得懂、说得清。'),
-          _ChoiceGroup<LearningGoal>(
-            title: '你的主要目标',
-            value: selectedGoal,
-            options: const {
-              LearningGoal.dailyLife: '日常生活',
-              LearningGoal.travel: '旅行',
-              LearningGoal.workStarter: '工作起步',
-            },
-            onChanged: (value) => setState(() => selectedGoal = value),
-          ),
           _ChoiceGroup<int>(
             title: '每天学习多久？',
             value: selectedMinutes,
@@ -91,9 +83,7 @@ class _WelcomePageState extends State<WelcomePage> {
           PrimaryButton(
             label: '继续',
             onPressed: () {
-              widget.state
-                ..setGoal(selectedGoal)
-                ..setDailyMinutes(selectedMinutes);
+              widget.state.setDailyMinutes(selectedMinutes);
               widget.onContinue();
             },
           ),
@@ -119,8 +109,25 @@ class PlacementPage extends StatefulWidget {
   State<PlacementPage> createState() => _PlacementPageState();
 }
 
-class _PlacementPageState extends State<PlacementPage> {
+enum _PlacementPhase { selfReport, listen, readAloud, answer, result }
+
+class _PlacementPageState extends State<PlacementPage>
+    with VoiceAnswerMixin<PlacementPage> {
+  static const _listeningText = 'Hello. My name is Mia. Nice to meet you.';
+  static const _listeningOptions = [
+    '你好，我叫 Mia，很高兴认识你。',
+    '你好，我来自 Mia，今天很开心。',
+    '再见，Mia，明天见。',
+  ];
+  static const _readAloudText = 'Hello. My name is ...';
+
   late PlacementLevel selected;
+  var phase = _PlacementPhase.selfReport;
+  int listeningChoice = -1;
+  final answerController = TextEditingController();
+
+  @override
+  AppState get voiceState => widget.state;
 
   @override
   void initState() {
@@ -128,52 +135,287 @@ class _PlacementPageState extends State<PlacementPage> {
     selected = widget.state.placement;
   }
 
+  @override
+  void dispose() {
+    VoiceService.instance.stopSpeaking();
+    disposeVoiceAnswer(keepRecording: false);
+    answerController.dispose();
+    super.dispose();
+  }
+
+  bool get _understoodGreeting => listeningChoice == 0;
+
+  bool get _answeredName =>
+      coreItemUsedIn('A0-P01', answerController.text.trim());
+
+  /// Placement only picks an A0 starting point until A1 content is frozen, and
+  /// it never marks a lesson as passed.
+  String get _suggestedLessonId =>
+      _understoodGreeting && _answeredName ? 'a0-02' : 'a0-01';
+
+  String get _reason => _understoodGreeting && _answeredName
+      ? '你已经能听懂问候，也能说出自己的名字，可以从拼写名字开始。'
+      : _understoodGreeting
+      ? '你能听懂问候，先把自我介绍说完整会更稳。'
+      : '先从问候和介绍名字开始，打好第一句的基础。';
+
+  void _back() {
+    VoiceService.instance.stopSpeaking();
+    switch (phase) {
+      case _PlacementPhase.selfReport:
+        widget.onBack?.call();
+      case _PlacementPhase.listen:
+        setState(() => phase = _PlacementPhase.selfReport);
+      case _PlacementPhase.readAloud:
+        setState(() => phase = _PlacementPhase.listen);
+      case _PlacementPhase.answer:
+        setState(() => phase = _PlacementPhase.readAloud);
+      case _PlacementPhase.result:
+        setState(() => phase = _PlacementPhase.answer);
+    }
+  }
+
+  void _startFrom(String lessonId) {
+    widget.state.setPlacementStartLesson(lessonId);
+    widget.onStart();
+  }
+
+  Future<void> _toggleVoiceAnswer() async {
+    if (aiVoiceRecording) {
+      await finishVoiceInput(
+        keepAudio: false,
+        onTranscript: (text) => answerController.text = text,
+      );
+      return;
+    }
+    await startVoiceInput();
+  }
+
   @override
   Widget build(BuildContext context) {
+    final showBack =
+        widget.onBack != null || phase != _PlacementPhase.selfReport;
+    return AppPage(
+      appBar: showBack
+          ? AppBar(
+              leading: IconButton(
+                icon: const Icon(Icons.arrow_back),
+                tooltip: "返回",
+                onPressed: _back,
+              ),
+              title: const Text("基础定位"),
+            )
+          : null,
+      child: switch (phase) {
+        _PlacementPhase.selfReport => _selfReport(context),
+        _PlacementPhase.listen => _listen(context),
+        _PlacementPhase.readAloud => _readAloud(context),
+        _PlacementPhase.answer => _answer(context),
+        _PlacementPhase.result => _result(context),
+      },
+    );
+  }
+
+  Widget _selfReport(BuildContext context) {
     const labels = {
       PlacementLevel.beginner: ('完全零基础', '从你好、自我介绍开始'),
       PlacementLevel.someBasics: ('能说一点', '认识常见单词或短句'),
       PlacementLevel.simpleConversation: ('能简单对话', '想说得更自然、更有信心'),
     };
-    return AppPage(
-      appBar: widget.onBack != null
-          ? AppBar(
-              leading: IconButton(
-                icon: const Icon(Icons.arrow_back),
-                tooltip: "返回",
-                onPressed: widget.onBack,
-              ),
-              title: const Text("基础定位"),
-            )
-          : null,
-      child: SpacedColumn(
-        spacing: 14,
-        children: [
-          const Eyebrow('第一步 · 约 3 分钟'),
-          Text('从哪里开始？', style: Theme.of(context).textTheme.headlineMedium),
-          const Text('选择最接近的状态，之后随时能调整。'),
-          for (final option in PlacementLevel.values)
-            _PlacementChoice(
-              option: option,
-              labels: labels[option]!,
-              isSelected: selected == option,
-              onTap: () => setState(() => selected = option),
-            ),
-          PrimaryButton(
-            label: '开始 3 分钟定位',
-            onPressed: () {
-              widget.state.setPlacement(selected);
-              widget.onStart();
-            },
+    return SpacedColumn(
+      spacing: 14,
+      children: [
+        const Eyebrow('第一步 · 约 3 分钟'),
+        Text('从哪里开始？', style: Theme.of(context).textTheme.headlineMedium),
+        const Text('选择最接近的状态，之后随时能调整。'),
+        for (final option in PlacementLevel.values)
+          _PlacementChoice(
+            option: option,
+            labels: labels[option]!,
+            isSelected: selected == option,
+            onTap: () => setState(() => selected = option),
           ),
+        PrimaryButton(
+          label: '开始 3 分钟定位',
+          onPressed: () {
+            widget.state.setPlacement(selected);
+            setState(() => phase = _PlacementPhase.listen);
+          },
+        ),
+        Center(
+          child: TextButton(
+            onPressed: () => _startFrom('a0-01'),
+            child: const Text('直接从第一课开始'),
+          ),
+        ),
+      ],
+    );
+  }
+
+  Widget _listen(BuildContext context) => SpacedColumn(
+    spacing: 14,
+    children: [
+      const Eyebrow('定位 · 1 / 3'),
+      Text('听一听，选出意思。', style: Theme.of(context).textTheme.headlineMedium),
+      SecondaryButton(
+        label: '播放句子',
+        onPressed: () => VoiceService.instance.speak(_listeningText),
+      ),
+      for (var index = 0; index < _listeningOptions.length; index++)
+        SectionCard(
+          tint: listeningChoice == index ? AppColors.softGreen : null,
+          onTap: () => setState(() => listeningChoice = index),
+          child: Row(
+            children: [
+              Icon(
+                listeningChoice == index
+                    ? Icons.radio_button_checked
+                    : Icons.radio_button_off,
+                color: listeningChoice == index
+                    ? AppColors.green
+                    : AppColors.muted,
+              ),
+              const SizedBox(width: 10),
+              Expanded(child: Text(_listeningOptions[index])),
+            ],
+          ),
+        ),
+      PrimaryButton(
+        label: '下一题',
+        onPressed: listeningChoice < 0
+            ? null
+            : () => setState(() => phase = _PlacementPhase.readAloud),
+      ),
+      Center(
+        child: TextButton(
+          onPressed: () => setState(() {
+            listeningChoice = -1;
+            phase = _PlacementPhase.readAloud;
+          }),
+          child: const Text('听不懂，下一题'),
+        ),
+      ),
+    ],
+  );
+
+  Widget _readAloud(BuildContext context) => SpacedColumn(
+    spacing: 14,
+    children: [
+      const Eyebrow('定位 · 2 / 3'),
+      Text('跟着读一句。', style: Theme.of(context).textTheme.headlineMedium),
+      const Text(
+        _readAloudText,
+        textAlign: TextAlign.center,
+        style: TextStyle(fontSize: 26, fontWeight: FontWeight.w600),
+      ),
+      SecondaryButton(
+        label: '播放示范音',
+        onPressed: () => VoiceService.instance.speak(_readAloudText),
+      ),
+      const SectionCard(
+        tint: AppColors.surfaceMuted,
+        child: Text('这一题只是开口热身，不录音、不打分，可以跳过。'),
+      ),
+      PrimaryButton(
+        label: '我读完了',
+        onPressed: () => setState(() => phase = _PlacementPhase.answer),
+      ),
+      Center(
+        child: TextButton(
+          onPressed: () => setState(() => phase = _PlacementPhase.answer),
+          child: const Text('现在不方便开口，跳过'),
+        ),
+      ),
+    ],
+  );
+
+  Widget _answer(BuildContext context) => SpacedColumn(
+    spacing: 14,
+    children: [
+      const Eyebrow('定位 · 3 / 3'),
+      Text('回答这个问题。', style: Theme.of(context).textTheme.headlineMedium),
+      SectionCard(
+        tint: AppColors.surfaceMuted,
+        child: Row(
+          children: [
+            const Expanded(
+              child: Text(
+                'What is your name?',
+                style: TextStyle(fontSize: 20, fontWeight: FontWeight.w600),
+              ),
+            ),
+            IconButton(
+              tooltip: '播放问题',
+              icon: const Icon(Icons.volume_up_outlined),
+              onPressed: () =>
+                  VoiceService.instance.speak('What is your name?'),
+            ),
+          ],
+        ),
+      ),
+      TextField(
+        controller: answerController,
+        decoration: const InputDecoration(hintText: '用英语输入你的回答'),
+        onChanged: (_) => setState(() {}),
+      ),
+      SecondaryButton(
+        label: transcribing ? '正在识别…' : (aiVoiceRecording ? '说完了，识别' : '用语音回答'),
+        onPressed: transcribing ? null : _toggleVoiceAnswer,
+      ),
+      PrimaryButton(
+        label: '查看建议',
+        onPressed: aiVoiceRecording || transcribing
+            ? null
+            : () => setState(() => phase = _PlacementPhase.result),
+      ),
+      Center(
+        child: TextButton(
+          onPressed: () => setState(() {
+            answerController.clear();
+            phase = _PlacementPhase.result;
+          }),
+          child: const Text('还不会说，查看建议'),
+        ),
+      ),
+    ],
+  );
+
+  Widget _result(BuildContext context) {
+    final lesson = lessonById(_suggestedLessonId);
+    return SpacedColumn(
+      spacing: 14,
+      children: [
+        const Eyebrow('定位结果'),
+        Text(
+          '建议从 A0 第 ${lesson.number} 课开始',
+          style: Theme.of(context).textTheme.headlineMedium,
+        ),
+        SectionCard(
+          tint: AppColors.softGreen,
+          child: SpacedColumn(
+            spacing: 6,
+            children: [
+              Text(
+                '第 ${lesson.number} 课 · ${lesson.title}',
+                style: const TextStyle(fontWeight: FontWeight.w600),
+              ),
+              Text(_reason),
+            ],
+          ),
+        ),
+        const Text('前面的课程随时可以回去学，定位不会跳过任何复习。'),
+        PrimaryButton(
+          label: '开始今天学习',
+          onPressed: () => _startFrom(_suggestedLessonId),
+        ),
+        if (_suggestedLessonId != 'a0-01')
           Center(
             child: TextButton(
-              onPressed: widget.onStart,
-              child: const Text('直接从第一课开始'),
+              onPressed: () => _startFrom('a0-01'),
+              child: const Text('从更简单内容开始'),
             ),
           ),
-        ],
-      ),
+      ],
     );
   }
 }

kouyu_english/lib/features/shell/learning_shell.dart

@@ -26,6 +26,7 @@ class _LearningShellState extends State<LearningShell> {
   var route = _ShellRoute.tab;
   _ShellRoute? previousRoute;
   bool dialogueInLesson = false;
+  String sceneId = 'a0-meet';
   AssessmentPack? assessmentPack;
   DialogueSummaryData? dialogueSummary;
 
@@ -45,9 +46,10 @@ class _LearningShellState extends State<LearningShell> {
     route = _ShellRoute.scene;
   });
 
-  void showDialogue({bool inLesson = false}) => setState(() {
+  void showDialogue({bool inLesson = false, String? scene}) => setState(() {
     previousRoute = route;
     dialogueInLesson = inLesson;
+    if (scene != null) sceneId = scene;
     route = _ShellRoute.dialogue;
   });
 
@@ -125,13 +127,16 @@ class _LearningShellState extends State<LearningShell> {
         );
       case _ShellRoute.scene:
         body = DialogueScenePage(
-          onStart: showDialogue,
+          state: widget.state,
+          onStart: (id) => showDialogue(scene: id),
           onBack: () => showTab(tab),
         );
       case _ShellRoute.dialogue:
         body = DialoguePage(
+          key: ValueKey(dialogueInLesson ? 'lesson' : 'scene-$sceneId'),
           state: widget.state,
           isLessonDialogue: dialogueInLesson,
+          sceneId: sceneId,
           onFinished: (summary) {
             if (dialogueInLesson) {
               showLesson();
@@ -147,7 +152,7 @@ class _LearningShellState extends State<LearningShell> {
           summary: dialogueSummary!,
           onHome: () => showTab(AppTab.home),
           onLesson: showLesson,
-          onRetry: showDialogue,
+          onRetry: () => showDialogue(scene: sceneId),
           onBack: () => showTab(tab),
         );
       case _ShellRoute.settings:
@@ -194,7 +199,8 @@ class _LearningShellState extends State<LearningShell> {
                   selectedIndex: tab.index,
                   height: 70,
                   indicatorColor: AppColors.softGreen,
-                  onDestinationSelected: (index) => showTab(AppTab.values[index]),
+                  onDestinationSelected: (index) =>
+                      showTab(AppTab.values[index]),
                   destinations: const [
                     NavigationDestination(
                       icon: Icon(Icons.home_outlined),
@@ -243,6 +249,16 @@ class _LearningShellState extends State<LearningShell> {
           },
           onOpenDialogue: showDialogueScene,
           onResumeLessonDialogue: () => showDialogue(inLesson: true),
+          onStartReinforcement: () {
+            widget.state.scheduleA0Reinforcement();
+            showTab(AppTab.review);
+          },
+          onOpenAssessment: (packId) {
+            final pack = a0AssessmentPacks
+                .where((item) => item.id == packId)
+                .firstOrNull;
+            if (pack != null) showAssessment(pack);
+          },
         );
       case AppTab.learn:
         return _LearningMap(
@@ -258,7 +274,10 @@ class _LearningShellState extends State<LearningShell> {
           state: widget.state,
         );
       case AppTab.dialogue:
-        return DialogueScenePage(onStart: showDialogue);
+        return DialogueScenePage(
+          state: widget.state,
+          onStart: (id) => showDialogue(scene: id),
+        );
       case AppTab.review:
         return ReviewPage(
           state: widget.state,