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/core/models.dart

@@ -78,9 +78,9 @@ enum ContentSource { builtInOriginal, aiGenerated, importedReference }
 class DialogueAiResponse {
   const DialogueAiResponse({
     required this.reply,
-    required this.slots,
-    required this.evidence,
-    required this.suggestsComplete,
+    this.slots = const {},
+    this.evidence = const [],
+    this.suggestsComplete = false,
     this.translation,
     this.feedback,
   });
@@ -210,6 +210,92 @@ class TemporaryLexiconEntry {
   final DateTime createdAt;
 }
 
+/// Represents an extracted key phrase or vocabulary item within a sentence.
+class PhraseBreakdownItem {
+  const PhraseBreakdownItem({
+    required this.phrase,
+    required this.meaning,
+    this.ipa,
+    this.usageNote,
+  });
+
+  final String phrase;
+  final String meaning;
+  final String? ipa;
+  final String? usageNote;
+
+  Map<String, dynamic> toJson() => {
+    'phrase': phrase,
+    'meaning': meaning,
+    if (ipa != null) 'ipa': ipa,
+    if (usageNote != null) 'usageNote': usageNote,
+  };
+
+  factory PhraseBreakdownItem.fromJson(Map<String, dynamic> json) =>
+      PhraseBreakdownItem(
+        phrase: json['phrase'] as String? ?? '',
+        meaning: json['meaning'] as String? ?? '',
+        ipa: json['ipa'] as String?,
+        usageNote: json['usageNote'] as String?,
+      );
+}
+
+/// Structured multi-dimensional analysis for a sentence or phrase, including
+/// translation, sentence pattern, grammar note, pronunciation tips, and extracted phrases.
+class SentenceAnalysisResult {
+  const SentenceAnalysisResult({
+    required this.originalText,
+    required this.translation,
+    this.sentencePattern,
+    this.grammarNote,
+    this.pronunciationTips,
+    this.phrases = const [],
+    this.provider = 'unknown',
+    this.model = '',
+    required this.createdAt,
+  });
+
+  final String originalText;
+  final String translation;
+  final String? sentencePattern;
+  final String? grammarNote;
+  final String? pronunciationTips;
+  final List<PhraseBreakdownItem> phrases;
+  final String provider;
+  final String model;
+  final DateTime createdAt;
+
+  Map<String, dynamic> toJson() => {
+    'originalText': originalText,
+    'translation': translation,
+    if (sentencePattern != null) 'sentencePattern': sentencePattern,
+    if (grammarNote != null) 'grammarNote': grammarNote,
+    if (pronunciationTips != null) 'pronunciationTips': pronunciationTips,
+    'phrases': phrases.map((p) => p.toJson()).toList(),
+    'provider': provider,
+    'model': model,
+    'createdAt': createdAt.toIso8601String(),
+  };
+
+  factory SentenceAnalysisResult.fromJson(Map<String, dynamic> json) =>
+      SentenceAnalysisResult(
+        originalText: json['originalText'] as String? ?? '',
+        translation: json['translation'] as String? ?? '',
+        sentencePattern: json['sentencePattern'] as String?,
+        grammarNote: json['grammarNote'] as String?,
+        pronunciationTips: json['pronunciationTips'] as String?,
+        phrases: (json['phrases'] as List<dynamic>? ?? const [])
+            .whereType<Map<String, dynamic>>()
+            .map(PhraseBreakdownItem.fromJson)
+            .toList(),
+        provider: json['provider'] as String? ?? 'unknown',
+        model: json['model'] as String? ?? '',
+        createdAt: json['createdAt'] != null
+            ? DateTime.tryParse(json['createdAt'] as String) ?? DateTime.now()
+            : DateTime.now(),
+      );
+}
+
 class ReviewItem {
   const ReviewItem({
     required this.id,
@@ -329,9 +415,14 @@ class DialogueSummaryData {
     required this.completedTasks,
     required this.personalSentence,
     required this.usedHelp,
+    this.improvement,
   });
 
   final List<String> completedTasks;
   final String personalSentence;
   final bool usedHelp;
+
+  /// One improvement point collected during the dialogue and shown only at the
+  /// end, per "对话中不逐句打断" in the conversation spec.
+  final String? improvement;
 }