fix(voice): reset modelSpeaking in cleanup to unblock mic on restart

If the session closes while Gemini is mid-speech, cleanup() left
state.modelSpeaking=true. The next startSession() would then drop all
mic audio in sendAudioChunk() until a model turn eventually flipped
the flag — effectively deaf until page reload.

Author: heavygee

web/src/realtime/GeminiLiveVoiceSession.tsx

@@ -59,6 +59,8 @@ function cleanup() {
         }
         state.ws = null
     }
+    // Always reset modelSpeaking so a restart doesn't begin with audio capture silenced
+    state.modelSpeaking = false
 }
 
 class GeminiLiveVoiceSessionImpl implements VoiceSession {