Fix: extend audio mutex to prevent concurrent initialization crashes

Previous fix protected WriteMessage() but missed Connect() calls. During
session transfers, multiple goroutines could simultaneously initialize the
audio playback system, causing SIGABRT crashes in jetkvm_audio_playback_init.

Extended inputSourceMutex to serialize both Connect() and WriteMessage()
operations, ensuring atomic state transitions and preventing concurrent
C library initialization.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

audio.go

@@ -14,7 +14,7 @@ import (
 var (
 	audioMutex         sync.Mutex
 	setAudioTrackMutex sync.Mutex // Prevents concurrent setAudioTrack() calls
-	inputSourceMutex   sync.Mutex // Serializes WriteMessage() calls to input source
+	inputSourceMutex   sync.Mutex // Serializes Connect() and WriteMessage() calls to input source
 	outputSource       audio.AudioSource
 	inputSource        atomic.Pointer[audio.AudioSource]
 	outputRelay        *audio.OutputRelay
@@ -132,7 +132,6 @@ func onWebRTCDisconnect() {
 }
 
 func setAudioTrack(audioTrack *webrtc.TrackLocalStaticSample) {
-	// Prevent concurrent calls to avoid creating multiple relays
 	setAudioTrackMutex.Lock()
 	defer setAudioTrackMutex.Unlock()
 
@@ -264,18 +263,20 @@ func handleInputTrackForSession(track *webrtc.TrackRemote) {
 			continue // No relay, drop frame but keep reading
 		}
 
+		inputSourceMutex.Lock()
+
 		if !(*source).IsConnected() {
 			if err := (*source).Connect(); err != nil {
+				inputSourceMutex.Unlock()
 				continue
 			}
 		}
 
-		// Serialize WriteMessage() to prevent concurrent session handlers from corrupting Opus decoder
-		inputSourceMutex.Lock()
 		if err := (*source).WriteMessage(0, opusData); err != nil {
 			audioLogger.Warn().Err(err).Msg("failed to write audio message")
 			(*source).Disconnect()
 		}
+
 		inputSourceMutex.Unlock()
 	}
 }