feat: A1 短材料复现本单元理解词，并加入黑夜模式

课程内容
- 重写全部 21 个 A1 单元的听读材料，把本单元理解词织进听/读文本，
  单元内理解词复现率从约 20% 提升到约 77%（各单元 56–96%）。
- 修正 U01 房间号与机场大巴同为 thirty 的撞车（改为 17/30/40）。
- 校验器容差按级别读取（A1 为 8%），materials 覆盖率、字数、
  选项子串等校验全部通过；course_content_test 通过。

黑夜模式
- app_theme 拆分明/暗两套调色板，AppColors 随亮度切换；
  main 用 theme/darkTheme/themeMode + builder 镜像已解析亮度；
  主题偏好持久化到快照；进度页新增“外观主题”切换。

文档
- COURSE-PACK-JSON.md 更新 A1 词池覆盖（840/933）与材料复现约定。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

kouyu_english/test/app_state_test.dart

@@ -4,6 +4,7 @@ import 'package:kouyu_english/core/a0_core.dart';
 import 'package:kouyu_english/core/assessment_bank.dart';
 import 'package:kouyu_english/core/generated_content.dart';
 import 'package:kouyu_english/core/models.dart';
+import 'package:kouyu_english/core/review_feedback.dart';
 import 'package:kouyu_english/core/seed_courses.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 
@@ -52,13 +53,15 @@ void main() {
       final item = state.dueReviews.single;
       expect(a0CoreItems, contains(item.id));
       expect(item.variantIndex, 1);
-      expect(item.prompt, contains('情境'));
+      // The first rotation turns the written recall into dictation.
+      expect(item.skill, dictationSkill);
+      expect(item.prompt, contains('听'));
     },
   );
 
   test('an approved AI variant remains tied to its original review item', () {
     final state = AppState();
-    state.reviewQueue.add(dueItem());
+    state.reviewQueue.add(dueItem().copyWith(skill: dictationSkill));
     state.applyGeneratedReviewVariant(
       const GeneratedReviewVariant(
         variantId: 'ai-1',
@@ -70,6 +73,7 @@ void main() {
 
     expect(state.reviewQueue.single.id, 'A0-P12');
     expect(state.reviewQueue.single.isAiGenerated, isTrue);
+    expect(state.reviewQueue.single.skill, isNot(dictationSkill));
   });
 
   test(
@@ -134,6 +138,17 @@ void main() {
         createdAt: DateTime.now().subtract(const Duration(days: 20)),
       ),
     );
+    state.attemptEvidence.add(
+      AttemptEvidence(
+        id: 'scene-use',
+        itemId: item.id,
+        taskId: 'dialogue-scene-a0-meet-0',
+        skill: '情境使用',
+        inputMode: 'text',
+        outcome: EvidenceKind.independentSuccess,
+        createdAt: DateTime.now().subtract(const Duration(days: 19)),
+      ),
+    );
 
     for (var index = 0; index < 4; index++) {
       final current = state.reviewQueue.firstWhere(
@@ -197,6 +212,22 @@ void main() {
       );
     }
 
+    // Reworded reviews alone only show recall, never use in a situation.
+    state.rebuildMasteryFromEvidence();
+    expect(state.mastery['A0-P12']!.checkpoint, 4);
+    expect(state.mastery['A0-P12']!.status, MasteryStatus.recall);
+
+    state.attemptEvidence.add(
+      AttemptEvidence(
+        id: 'scene-use',
+        itemId: 'A0-P12',
+        taskId: 'dialogue-scene-a0-meet-1',
+        skill: '情境使用',
+        inputMode: 'text',
+        outcome: EvidenceKind.independentSuccess,
+        createdAt: base,
+      ),
+    );
     state.rebuildMasteryFromEvidence();
 
     expect(state.mastery['A0-P12']!.checkpoint, 4);
@@ -946,10 +977,17 @@ void main() {
     expect(
       matchesSegmentIndependent(
         'a0-10-a',
-        "I'm Mia. I'm from Guangzhou. I like tea. Do you like tea?",
+        "Please say that again. I'm Mia. I like water. Do you like tea?",
       ),
       isTrue,
     );
+    expect(
+      matchesSegmentIndependent(
+        'a0-10-a',
+        "I'm Mia. I'm from Guangzhou. I like tea. Do you like tea?",
+      ),
+      isFalse,
+    );
   });
 
   test('each free scene keeps its own daily recap', () {
@@ -1370,4 +1408,54 @@ void main() {
     expect(restored.dialogueDraft!.turns, hasLength(2));
     expect(restored.dialogueDraft!.turns.last.isLearner, isTrue);
   });
+
+  test('a spoken review answer keeps its transcript and input mode', () {
+    final state = AppState();
+    state.reviewQueue.add(dueItem());
+    state.completeReview(
+      state.reviewQueue.single,
+      assisted: false,
+      rawAnswer: "I'm from Hong Kong.",
+      inputMode: 'speechToText',
+      originalTranscript: "I'm from Hong Kong.",
+    );
+    final spoken = state.attemptEvidence.last;
+    expect(spoken.inputMode, 'speechToText');
+    expect(spoken.transcriptConfirmed, isTrue);
+    expect(spoken.transcriptEdited, isFalse);
+
+    final typed = AppState();
+    typed.reviewQueue.add(dueItem());
+    typed.completeReview(
+      typed.reviewQueue.single,
+      assisted: false,
+      rawAnswer: "I'm from Guangzhou.",
+      originalTranscript: "I'm from one show.",
+    );
+    expect(typed.attemptEvidence.last.inputMode, 'text');
+    expect(typed.attemptEvidence.last.transcriptEdited, isTrue);
+  });
+
+  test('each lesson practises the core items it targets', () {
+    for (final entry in a0TargetItemIdsByLesson.entries) {
+      final segments = lessonById(entry.key).segments;
+      final text = [
+        for (final segment in segments) ...[
+          activityBySegmentId(segment.id, entry.key).listening,
+          activityBySegmentId(segment.id, entry.key).speaking,
+          activityBySegmentId(segment.id, entry.key).reading,
+          activityBySegmentId(segment.id, entry.key).writingExample,
+          for (final item in vocabularyBySegmentId(segment.id, entry.key))
+            '${item.word}\n${item.example}',
+        ],
+      ].join('\n');
+      for (final id in entry.value) {
+        expect(
+          coreItemUsedIn(id, text, word: a0CoreItems[id]),
+          isTrue,
+          reason: '${entry.key} → $id ${a0CoreItems[id]}',
+        );
+      }
+    }
+  });
 }