feat: 完善听力口语辅助状态记录、练习分块与复习抽查间隔机制

kouyu_english/lib/core/courses/assessment.dart

@@ -22,7 +22,9 @@ class AssessmentTask {
     skill: AssessmentSkill.values.byName(json['skill'] as String),
     prompt: json['prompt'] as String? ?? '',
     audio: json['audio'] as String?,
-    choices: [for (final choice in json['choices'] as List? ?? const []) '$choice'],
+    choices: [
+      for (final choice in json['choices'] as List? ?? const []) '$choice',
+    ],
     answerIndex: json['answerIndex'] as int?,
     accept: [
       for (final group in json['accept'] as List? ?? const [])
@@ -102,10 +104,7 @@ AssessmentPack? replacementFor(String packId) =>
 /// The pack whose results [packId] counts toward: the original of a
 /// replacement pack, otherwise [packId] itself.
 String canonicalAssessmentPackId(String packId) =>
-    assessmentPacks
-        .where((pack) => pack.id == packId)
-        .firstOrNull
-        ?.replaces ??
+    assessmentPacks.where((pack) => pack.id == packId).firstOrNull?.replaces ??
     packId;
 
 /// Local check of an open task with the same rule engine as the lessons: it

kouyu_english/lib/core/courses/core_items.dart

@@ -63,13 +63,7 @@ void registerSavedWord(
   required String zh,
   required String level,
 }) {
-  receptiveWordRegistry[id] = (
-    level: level,
-    unit: '',
-    en: en,
-    zh: zh,
-    ipa: '',
-  );
+  receptiveWordRegistry[id] = (level: level, unit: '', en: en, zh: zh, ipa: '');
 }
 
 /// Registers one word of the standalone word bank. Unlike a unit's receptive
@@ -191,9 +185,10 @@ WordQuestion? receptiveQuestion(
   if (wrong.isEmpty) return null;
   // A different variant asks the same word against other meanings, which is
   // what 「换题、换语境」 means for a word this small.
-  final rotated = [...wrong.skip(variant % wrong.length), ...wrong.take(variant % wrong.length)]
-      .take(2)
-      .toList();
+  final rotated = [
+    ...wrong.skip(variant % wrong.length),
+    ...wrong.take(variant % wrong.length),
+  ].take(2).toList();
   // Asked from the meaning, the options are spellings and the prompt is the
   // Chinese; asked either other way, it is the other way round.
   final asksSpelling = mode == WordAskMode.recall;
@@ -339,7 +334,6 @@ const spokenRecallSkill = '口头回忆';
 /// review. Passing it is 「认识」 evidence and never advances a checkpoint.
 const recognitionGateSkill = '听辨识别';
 
-
 /// The skill of a contrast question: a situation is described and the learner
 /// picks which taught sentence it calls for. It shows the learner knows *when*
 /// to say something, which is not the same as being able to produce it, so it

kouyu_english/lib/core/courses/course_models.dart

@@ -12,7 +12,6 @@ class LessonSegment {
     this.estimatedMinutes = 12,
   });
 
-
   final String id;
   final List<String> targetItemIds;
   final List<String> previewItemIds;
@@ -86,8 +85,12 @@ class LessonActivity {
     required this.listening,
     required this.listeningQuestion,
     required this.answers,
+    this.listeningItemIds = const [],
     required this.speaking,
     this.speakingTip = '',
+    this.speakingChunks = const [],
+    this.speakingItemIds = const [],
+    this.speakingExamples = const [],
     required this.reading,
     required this.readingQuestion,
     required this.readingAnswer,
@@ -100,14 +103,17 @@ class LessonActivity {
     required this.independentHelp,
   });
 
-
   final String listening;
   final String listeningQuestion;
   final List<String> answers;
+  final List<String> listeningItemIds;
   final String speaking;
 
   /// 这句跟读的发音提示；为空时不显示，避免给每一句套用同一条提示。
   final String speakingTip;
+  final List<String> speakingChunks;
+  final List<String> speakingItemIds;
+  final List<String> speakingExamples;
   final String reading;
   final String readingQuestion;
   final String readingAnswer;
@@ -135,7 +141,6 @@ class LessonDialogue {
     this.taskLabels = const [],
   });
 
-
   final String goal;
   final List<String> prompts;
   final List<String> hints;
@@ -165,7 +170,6 @@ class DialogueScene {
     this.unlockAfterLessonId,
   });
 
-
   final String id;
   final String title;
   final String summary;

kouyu_english/lib/core/courses/course_pack.dart

@@ -214,8 +214,12 @@ class PackSegment {
     required this.listeningText,
     required this.listeningQuestion,
     required this.listeningOptions,
+    this.listeningItemIds = const [],
     required this.speakingText,
     required this.speakingTip,
+    this.speakingChunks = const [],
+    this.speakingItemIds = const [],
+    this.speakingExamples = const [],
     required this.readingText,
     required this.readingQuestion,
     required this.readingOptions,
@@ -241,9 +245,13 @@ class PackSegment {
   final String listeningText;
   final String listeningQuestion;
   final List<String> listeningOptions;
+  final List<String> listeningItemIds;
 
   final String speakingText;
   final String speakingTip;
+  final List<String> speakingChunks;
+  final List<String> speakingItemIds;
+  final List<String> speakingExamples;
 
   final String readingText;
   final String readingQuestion;
@@ -288,8 +296,15 @@ class PackSegment {
       listeningText: listening['text'] as String? ?? '',
       listeningQuestion: listening['question'] as String? ?? '',
       listeningOptions: _stringList(listening['options']),
+      listeningItemIds: _stringList(listening['itemIds']),
       speakingText: firstSpeaking['text'] as String? ?? '',
       speakingTip: firstSpeaking['tip'] as String? ?? '',
+      speakingChunks: _stringList(firstSpeaking['chunks']),
+      speakingItemIds: _stringList(firstSpeaking['itemIds']),
+      speakingExamples: [
+        for (final line in speaking.skip(1))
+          if (line['text'] is String) line['text'] as String,
+      ],
       readingText: reading['text'] as String? ?? '',
       readingQuestion: reading['question'] as String? ?? '',
       readingOptions: _stringList(reading['options']),

kouyu_english/lib/core/courses/course_repository.dart

@@ -225,8 +225,12 @@ class CourseRepository {
         answers: seg.listeningOptions.isNotEmpty
             ? seg.listeningOptions
             : const [''],
+        listeningItemIds: seg.listeningItemIds,
         speaking: seg.speakingText,
         speakingTip: seg.speakingTip,
+        speakingChunks: seg.speakingChunks,
+        speakingItemIds: seg.speakingItemIds,
+        speakingExamples: seg.speakingExamples,
         reading: seg.readingText,
         readingQuestion: seg.readingQuestion,
         readingAnswer: seg.readingOptions.isNotEmpty