Preserve dictation recordings across WebSocket interruptions (#3159)

* fix(app): preserve dictation audio across transport failures

Keep captured PCM in the existing local segment buffer when a WebSocket send fails. Finish only after server acknowledgements and fail an idle drain so the retry path can resend the complete recording.

* fix(app): dispose dictation stream sender cleanly

packages/app/src/hooks/use-dictation.ts

@@ -449,6 +449,7 @@ export function useDictation(options: UseDictationOptions): UseDictationResult {
       attemptGuard.cancel();
       stopDurationTracking();
       void audioStop.current().catch(() => undefined);
+      senderRef.current?.dispose();
     };
   }, [stopDurationTracking]);