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/features/onboarding/onboarding_pages.dart

@@ -147,13 +147,21 @@ class _PlacementPageState extends State<PlacementPage>
   bool get _answeredName =>
       coreItemUsedIn('A0-P01', answerController.text.trim());
 
-  /// Placement only picks an A0 starting point until A1 content is frozen, and
-  /// it never marks a lesson as passed.
-  String get _suggestedLessonId =>
-      _understoodGreeting && _answeredName ? 'a0-02' : 'a0-01';
+  /// Self report only moves the starting point when both short checks pass.
+  /// Placement never marks the earlier lessons as completed.
+  String get _suggestedLessonId {
+    if (!_understoodGreeting || !_answeredName) return 'a0-01';
+    return switch (selected) {
+      PlacementLevel.beginner => 'a0-02',
+      PlacementLevel.someBasics => 'a0-03',
+      PlacementLevel.simpleConversation => 'a0-04',
+    };
+  }
 
   String get _reason => _understoodGreeting && _answeredName
-      ? '你已经能听懂问候，也能说出自己的名字，可以从拼写名字开始。'
+      ? selected == PlacementLevel.beginner
+            ? '你已经能听懂问候，也能说出自己的名字，可以从拼写名字开始。'
+            : '你通过了两项基础检查，结合自选基础，建议从这课试学；前面的课随时可以返回。'
       : _understoodGreeting
       ? '你能听懂问候，先把自我介绍说完整会更稳。'
       : '先从问候和介绍名字开始，打好第一句的基础。';