fix: 修复麦克风关闭后重新打开无法使用的问题

- 关闭麦克风时同时停止 VAD
- 打开麦克风时重新初始化 VAD

frontend/src/hooks/useVisionSession.ts

@@ -336,13 +336,17 @@ export function useVisionSession() {
   /** 麦克风开关 */
   const toggleMic = useCallback(async () => {
     if (isMicOn) {
+      await stopVAD();
       stopMic();
       setIsMicOn(false);
     } else {
       const micStream = await startMic();
-      setIsMicOn(!!micStream);
+      if (micStream) {
+        await startVAD(micStream);
+        setIsMicOn(true);
+      }
     }
-  }, [isMicOn, startMic, stopMic]);
+  }, [isMicOn, startMic, stopMic, startVAD, stopVAD]);
 
   /** 打断当前回复 */
   const interrupt = useCallback(() => {