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/lib/features/lesson/lesson_flow.dart

@@ -5,6 +5,7 @@ import '../../core/ai_service.dart';
 import '../../core/app_theme.dart';
 import '../../core/models.dart';
 import '../../core/seed_courses.dart';
+import '../../core/speech_compare.dart';
 import '../../core/voice_service.dart';
 import '../../core/writing_feedback.dart';
 import '../../widgets/app_widgets.dart';
@@ -112,6 +113,7 @@ class _LessonFlowState extends State<LessonFlow> {
           correctAnswer: activity.answers.first,
           selectedAnswer: selectedAnswer,
           audioPlayed: listeningAudioPlayed,
+          missed: listeningMissed,
           onSelected: (value) => setState(() {
             selectedAnswer = value;
             if (listeningOptions[value] != activity.answers.first) {
@@ -119,11 +121,14 @@ class _LessonFlowState extends State<LessonFlow> {
             }
           }),
           onPlayed: () => setState(() => listeningAudioPlayed = true),
-          onLookup: () => showLexiconLookup(
-            context,
-            state: widget.state,
-            initialText: activity.listening,
-          ),
+          onLookup: () {
+            setState(() => listeningMissed = true);
+            showLexiconLookup(
+              context,
+              state: widget.state,
+              initialText: activity.listening,
+            );
+          },
           onContinue:
               selectedAnswer >= 0 &&
                   listeningOptions[selectedAnswer] == activity.answers.first
@@ -135,6 +140,7 @@ class _LessonFlowState extends State<LessonFlow> {
         content = _SpeakingStep(
           state: widget.state,
           text: activity.speaking,
+          tip: activity.speakingTip,
           keepRecording: widget.state.keepRecordings,
           onContinue: widget.state.completeSpeaking,
         );