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/features/assessment/assessment_page.dart

@@ -158,6 +158,12 @@ class _AssessmentPageState extends State<AssessmentPage> {
 
   @override
   void dispose() {
+    VoiceService.instance.stopSpeaking();
+    VoiceService.instance.stopListening();
+    VoiceService.instance.stopRecordingPlayback();
+    if (listening || aiVoiceRecording) {
+      VoiceService.instance.stopRecording();
+    }
     controller.dispose();
     super.dispose();
   }
@@ -209,58 +215,22 @@ class _AssessmentPageState extends State<AssessmentPage> {
       return;
     }
 
-    if (listening) {
-      await VoiceService.instance.stopListening();
-      if (mounted) setState(() => listening = false);
-      return;
-    }
-    final ready = await VoiceService.instance.startListening(
-      (text, _) {
-        if (mounted) {
-          setState(() {
-            controller.text = text;
-            usedMic = true;
-            lastTranscript = text;
-            transcriptEdited = false;
-          });
-        }
-      },
-      onStatus: (status) {
-        if (mounted && (status == 'notListening' || status == 'done')) {
-          setState(() => listening = false);
-        }
-      },
-      onError: (err) {
-        if (mounted) {
-          setState(() => listening = false);
-        }
-      },
-    );
-    if (!ready) {
-      final recordStarted = await VoiceService.instance.startRecording();
-      if (mounted) {
-        setState(() {
-          aiVoiceRecording = recordStarted;
-          listening = recordStarted;
-          speakingUnavailable = !recordStarted;
-        });
-        if (recordStarted) {
-          ScaffoldMessenger.of(context).showSnackBar(
-            const SnackBar(content: Text('已启动麦克风录音，回答后再次点击，AI 将自动转写为英文。')),
-          );
-        } else {
-          ScaffoldMessenger.of(context).showSnackBar(
-            const SnackBar(content: Text('无法访问麦克风，口语可稍后补测。')),
-          );
-        }
-      }
-      return;
-    }
-    if (mounted) {
-      setState(() {
-        listening = ready;
-        speakingUnavailable = !ready;
-      });
+    VoiceService.instance.stopSpeaking();
+    final recordStarted = await VoiceService.instance.startRecording();
+    if (!mounted) return;
+    setState(() {
+      aiVoiceRecording = recordStarted;
+      listening = recordStarted;
+      speakingUnavailable = !recordStarted;
+    });
+    if (recordStarted) {
+      ScaffoldMessenger.of(context).showSnackBar(
+        const SnackBar(content: Text('已启动麦克风录音，回答后再次点击，将自动转写为英文。')),
+      );
+    } else {
+      ScaffoldMessenger.of(context).showSnackBar(
+        const SnackBar(content: Text('无法访问麦克风，口语可稍后补测。')),
+      );
     }
   }