feat: 重做阅读找答案题与 AI 情境对话，并归拢本地识别、查词等既有改动

阅读"在对话里找到答案"：
- 16 道题全部重写，干扰项真实出现在对话里，靠说话人归属或否定句才能作答
- 选项按题目内容确定性打乱，答案不再固定排第一；听力环节同样处理
- 去掉超纲干扰项、重复题干，收紧自由作答匹配（过去单个字母也能判对）

AI 情境对话：
- 提示词区分"AI 这一句要做什么"与"学习者随后要完成什么"，并下发已教词句清单
- JSON 只强制 reply，translation/feedback 可选；不再索要用不上的 slots/evidence
- AI 不可用时页面明确提示当前回复来自内置示范脚本
- 删掉按 stage 下标猜中文翻译的兜底，避免译文与英文对不上
- 整课对话改用逐轮必需表达校验，替换"关键词沾边就算过"；修正自由场景正则误伤
- 总结的"完成任务"按实际通过的轮次生成；模型点评只在结束页呈现一次
- 自由场景支持草稿续练（独立存储槽）；修正回答轮数文案与永不解锁的场景标注

同时提交此前工作区中累积的改动：SenseVoice 本地识别、查词/句型解析卡、
复习与测评页调整等，并补充对话校验、选项分布和句子解析的测试。

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

kouyu_english/lib/features/lesson/lesson_flow.dart

@@ -89,9 +89,15 @@ class _LessonFlowState extends State<LessonFlow> {
           onSkip: widget.state.completePreview,
         );
       case LessonStep.listening:
+        final listeningOptions = shuffledOptions(
+          activity.answers,
+          '${activity.listening}-listening',
+        );
         content = _ListeningStep(
           state: widget.state,
           activity: activity,
+          options: listeningOptions,
+          correctAnswer: activity.answers.first,
           selectedAnswer: selectedAnswer,
           audioPlayed: listeningAudioPlayed,
           onSelected: (value) => setState(() => selectedAnswer = value),
@@ -101,7 +107,9 @@ class _LessonFlowState extends State<LessonFlow> {
             state: widget.state,
             initialText: activity.listening,
           ),
-          onContinue: selectedAnswer == 0
+          onContinue:
+              selectedAnswer >= 0 &&
+                  listeningOptions[selectedAnswer] == activity.answers.first
               ? widget.state.completeListening
               : null,
         );
@@ -333,6 +341,8 @@ class _ListeningStep extends StatelessWidget {
   const _ListeningStep({
     required this.state,
     required this.activity,
+    required this.options,
+    required this.correctAnswer,
     required this.selectedAnswer,
     required this.audioPlayed,
     required this.onSelected,
@@ -343,6 +353,8 @@ class _ListeningStep extends StatelessWidget {
 
   final LessonActivity activity;
   final AppState state;
+  final List<String> options;
+  final String correctAnswer;
 
   final int selectedAnswer;
   final bool audioPlayed;
@@ -353,7 +365,7 @@ class _ListeningStep extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final answers = activity.answers;
+    final answers = options;
     return _LessonScaffold(
       step: 2,
       child: SpacedColumn(
@@ -409,7 +421,7 @@ class _ListeningStep extends StatelessWidget {
                 : (audioPlayed ? '请选择答案' : '先播放音频或选择答案'),
             onPressed: onContinue,
           ),
-          if (selectedAnswer >= 0 && selectedAnswer != 0)
+          if (selectedAnswer >= 0 && answers[selectedAnswer] != correctAnswer)
             const Text(
               '再听一次，选择正确答案。',
               style: TextStyle(color: AppColors.warmInk),
@@ -645,77 +657,299 @@ class _ReadingStep extends StatefulWidget {
 
 class _ReadingStepState extends State<_ReadingStep> {
   final controller = TextEditingController();
+  int? selectedOptionIndex;
   bool showAnswer = false;
 
+  /// 打乱后的选项：答案不再固定排在第一位，但同一道题顺序保持稳定。
+  late final List<String> options = shuffledOptions(
+    widget.activity.readingOptions,
+    '${widget.activity.readingQuestion}-reading',
+  );
+
   @override
   void dispose() {
     controller.dispose();
     super.dispose();
   }
 
+  bool _isOptionCorrect(int index) {
+    if (options.isEmpty || index < 0 || index >= options.length) {
+      return false;
+    }
+    final option = options[index].trim();
+    final answer = widget.activity.readingAnswer.trim();
+    if (option.toLowerCase() == answer.toLowerCase()) return true;
+
+    final normOption = option
+        .toLowerCase()
+        .replaceAll(RegExp(r'[^a-z0-9\u4e00-\u9fa5]'), '');
+    final normAnswer = answer
+        .toLowerCase()
+        .replaceAll(RegExp(r'[^a-z0-9\u4e00-\u9fa5]'), '');
+    return normOption.isNotEmpty &&
+        normAnswer.isNotEmpty &&
+        (normOption.contains(normAnswer) || normAnswer.contains(normOption));
+  }
+
+  bool get isOptionMode => options.isNotEmpty;
+
   bool get isCorrect {
+    if (isOptionMode) {
+      return selectedOptionIndex != null && _isOptionCorrect(selectedOptionIndex!);
+    }
     final answer = widget.activity.readingAnswer.toLowerCase().replaceAll(
-      RegExp(r'[^a-z0-9]'),
+      RegExp(r'[^a-z0-9\u4e00-\u9fa5]'),
       '',
     );
     final response = controller.text.toLowerCase().replaceAll(
-      RegExp(r'[^a-z0-9]'),
+      RegExp(r'[^a-z0-9\u4e00-\u9fa5]'),
       '',
     );
-    return response.isNotEmpty && response.contains(answer);
+    // 只接受写全了答案的输入：过去反向的 answer.contains(response) 让单个字母
+    // 也能判对（'a' 通过 'A book'）。
+    return response.isNotEmpty && answer.isNotEmpty && response.contains(answer);
   }
 
   @override
-  Widget build(BuildContext context) => _LessonScaffold(
-    step: 4,
-    child: SpacedColumn(
-      children: [
-        const Eyebrow('读一读'),
-        Text('在对话里找到答案。', style: Theme.of(context).textTheme.headlineMedium),
-        SectionCard(
-          tint: AppColors.softGreen,
-          child: LexiconText(
-            widget.activity.reading,
-            state: widget.state,
-            style: TextStyle(fontSize: 16, height: 1.6),
-          ),
-        ),
-        Text(widget.activity.readingQuestion),
-        TextButton.icon(
-          onPressed: widget.onLookup,
-          icon: const Icon(Icons.menu_book_outlined),
-          label: const Text('查词或短语'),
-        ),
-        TextField(
-          controller: controller,
-          onChanged: (_) => setState(() {}),
-          decoration: const InputDecoration(
-            hintText: '用英文输入答案',
-            filled: true,
-            fillColor: AppColors.surface,
-            border: OutlineInputBorder(),
-          ),
-        ),
-        if (showAnswer)
+  Widget build(BuildContext context) {
+    final hasSelected = selectedOptionIndex != null;
+    final answeredCorrectly = isCorrect;
+
+    return _LessonScaffold(
+      step: 4,
+      child: SpacedColumn(
+        children: [
+          const Eyebrow('读一读'),
+          Text('在对话里找到答案。', style: Theme.of(context).textTheme.headlineMedium),
           SectionCard(
-            tint: AppColors.warm,
-            child: Text(
-              '答案：${widget.activity.readingAnswer}',
-              style: const TextStyle(color: AppColors.warmInk),
+            tint: AppColors.softGreen,
+            child: Column(
+              crossAxisAlignment: CrossAxisAlignment.start,
+              children: [
+                Row(
+                  mainAxisAlignment: MainAxisAlignment.spaceBetween,
+                  children: [
+                    const Row(
+                      children: [
+                        Icon(Icons.chat_bubble_outline, size: 16, color: AppColors.green),
+                        SizedBox(width: 6),
+                        Text(
+                          '对话内容',
+                          style: TextStyle(
+                            fontSize: 13,
+                            fontWeight: FontWeight.w600,
+                            color: AppColors.green,
+                          ),
+                        ),
+                      ],
+                    ),
+                    InkWell(
+                      onTap: () => VoiceService.instance.speak(widget.activity.reading),
+                      borderRadius: BorderRadius.circular(16),
+                      child: const Padding(
+                        padding: EdgeInsets.symmetric(horizontal: 8, vertical: 4),
+                        child: Row(
+                          children: [
+                            Icon(Icons.volume_up_outlined, size: 16, color: AppColors.green),
+                            SizedBox(width: 4),
+                            Text('朗读对话', style: TextStyle(fontSize: 13, color: AppColors.green)),
+                          ],
+                        ),
+                      ),
+                    ),
+                  ],
+                ),
+                const SizedBox(height: 8),
+                LexiconText(
+                  widget.activity.reading,
+                  state: widget.state,
+                  style: const TextStyle(fontSize: 16, height: 1.6),
+                ),
+              ],
             ),
           ),
-        if (!showAnswer && controller.text.isNotEmpty && !isCorrect)
-          TextButton(
-            onPressed: () => setState(() => showAnswer = true),
-            child: const Text('查看答案后继续学习'),
+          Row(
+            children: [
+              TextButton.icon(
+                onPressed: widget.onLookup,
+                icon: const Icon(Icons.menu_book_outlined, size: 18),
+                label: const Text('查词或短语'),
+              ),
+              const SizedBox(width: 8),
+              TextButton.icon(
+                onPressed: () {
+                  final lines = widget.activity.reading.split('\n');
+                  final target = lines.firstWhere(
+                    (l) => l.trim().isNotEmpty,
+                    orElse: () => widget.activity.reading,
+                  ).replaceFirst(RegExp(r'^[A-Za-z]+:\s*'), '');
+                  showLexiconLookup(
+                    context,
+                    state: widget.state,
+                    initialText: target,
+                  );
+                },
+                icon: const Icon(Icons.auto_stories_outlined, size: 18),
+                label: const Text('句型深度解析'),
+              ),
+            ],
           ),
-        PrimaryButton(
-          label: showAnswer ? '继续写一写' : '检查并继续',
-          onPressed: showAnswer || isCorrect ? widget.onContinue : null,
-        ),
-      ],
-    ),
-  );
+          SectionCard(
+            tint: AppColors.surfaceMuted,
+            child: Row(
+              crossAxisAlignment: CrossAxisAlignment.start,
+              children: [
+                Container(
+                  padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 2),
+                  decoration: BoxDecoration(
+                    color: AppColors.green.withValues(alpha: 0.12),
+                    borderRadius: BorderRadius.circular(6),
+                  ),
+                  child: const Text(
+                    '问题',
+                    style: TextStyle(
+                      color: AppColors.green,
+                      fontWeight: FontWeight.bold,
+                      fontSize: 12,
+                    ),
+                  ),
+                ),
+                const SizedBox(width: 10),
+                Expanded(
+                  child: Text(
+                    widget.activity.readingQuestion,
+                    style: const TextStyle(
+                      fontSize: 15,
+                      fontWeight: FontWeight.w600,
+                      color: AppColors.ink,
+                    ),
+                  ),
+                ),
+              ],
+            ),
+          ),
+          if (isOptionMode) ...[
+            for (var index = 0; index < options.length; index++) ...[
+              SectionCard(
+                tint: selectedOptionIndex == index
+                    ? (_isOptionCorrect(index) ? AppColors.softGreen : AppColors.warm)
+                    : null,
+                onTap: () {
+                  setState(() {
+                    selectedOptionIndex = index;
+                    showAnswer = false;
+                  });
+                },
+                child: Row(
+                  children: [
+                    Icon(
+                      selectedOptionIndex == index
+                          ? (_isOptionCorrect(index) ? Icons.check_circle : Icons.cancel_outlined)
+                          : Icons.radio_button_off,
+                      color: selectedOptionIndex == index
+                          ? (_isOptionCorrect(index) ? AppColors.green : AppColors.warmInk)
+                          : AppColors.muted,
+                    ),
+                    const SizedBox(width: 12),
+                    Expanded(
+                      child: Text(
+                        options[index],
+                        style: TextStyle(
+                          fontSize: 15,
+                          fontWeight: selectedOptionIndex == index ? FontWeight.w600 : FontWeight.normal,
+                          color: selectedOptionIndex == index
+                              ? (_isOptionCorrect(index) ? AppColors.green : AppColors.warmInk)
+                              : AppColors.ink,
+                        ),
+                      ),
+                    ),
+                  ],
+                ),
+              ),
+            ],
+            if (hasSelected && answeredCorrectly)
+              Container(
+                padding: const EdgeInsets.symmetric(horizontal: 14, vertical: 10),
+                decoration: BoxDecoration(
+                  color: AppColors.softGreen,
+                  borderRadius: BorderRadius.circular(10),
+                  border: Border.all(color: AppColors.green.withValues(alpha: 0.3)),
+                ),
+                child: const Row(
+                  children: [
+                    Icon(Icons.check_circle, color: AppColors.green, size: 20),
+                    SizedBox(width: 8),
+                    Expanded(
+                      child: Text(
+                        '回答正确！点击下方按钮继续',
+                        style: TextStyle(
+                          color: AppColors.green,
+                          fontWeight: FontWeight.w600,
+                          fontSize: 14,
+                        ),
+                      ),
+                    ),
+                  ],
+                ),
+              )
+            else if (hasSelected && !answeredCorrectly)
+              Container(
+                padding: const EdgeInsets.symmetric(horizontal: 14, vertical: 10),
+                decoration: BoxDecoration(
+                  color: AppColors.warm,
+                  borderRadius: BorderRadius.circular(10),
+                  border: Border.all(color: AppColors.warmInk.withValues(alpha: 0.2)),
+                ),
+                child: const Row(
+                  children: [
+                    Icon(Icons.help_outline, color: AppColors.warmInk, size: 20),
+                    SizedBox(width: 8),
+                    Expanded(
+                      child: Text(
+                        '不对哦，再仔细观察对话中的关键句子～',
+                        style: TextStyle(color: AppColors.warmInk, fontSize: 13),
+                      ),
+                    ),
+                  ],
+                ),
+              ),
+          ] else ...[
+            TextField(
+              controller: controller,
+              onChanged: (_) => setState(() {}),
+              decoration: const InputDecoration(
+                hintText: '用英文输入答案',
+                filled: true,
+                fillColor: AppColors.surface,
+                border: OutlineInputBorder(),
+              ),
+            ),
+          ],
+          if (showAnswer)
+            SectionCard(
+              tint: AppColors.warm,
+              child: Text(
+                '答案：${widget.activity.readingAnswer}',
+                style: const TextStyle(color: AppColors.warmInk),
+              ),
+            ),
+          if (!showAnswer &&
+              ((isOptionMode && hasSelected && !answeredCorrectly) ||
+                  (!isOptionMode && controller.text.isNotEmpty && !answeredCorrectly)))
+            TextButton(
+              onPressed: () => setState(() => showAnswer = true),
+              child: const Text('查看答案后继续学习'),
+            ),
+          PrimaryButton(
+            label: showAnswer || answeredCorrectly
+                ? '继续写一写'
+                : (isOptionMode ? '请选择答案' : '检查并继续'),
+            onPressed: showAnswer || answeredCorrectly ? widget.onContinue : null,
+          ),
+        ],
+      ),
+    );
+  }
 }
 
 class _WritingStep extends StatefulWidget {