Add desktop mute toggle button in draft board

Add a setMute WebSocket action and a mute IconButton in the draft
board title bar. The button optimistically flips local state and
rolls back with a toast when the desktop is unreachable.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/main.dart

@@ -134,6 +134,13 @@ class NativeConnectionApi {
     return result ?? false;
   }
 
+  Future<bool> sendMute(bool muted) async {
+    final result = await _methodChannel.invokeMethod<bool>('sendMute', {
+      'muted': muted,
+    });
+    return result ?? false;
+  }
+
   Future<List<DiscoveredDevice>> startDiscovery() async {
     try {
       final result = await _methodChannel.invokeListMethod<dynamic>(
@@ -184,6 +191,7 @@ class _InputSyncPageState extends State<InputSyncPage>
   bool headerExpanded = true;
   bool inputFocused = false;
   bool scanning = false;
+  bool desktopMuted = false;
 
   @override
   void initState() {
@@ -265,6 +273,7 @@ class _InputSyncPageState extends State<InputSyncPage>
         }
         if (!nextState.connected) {
           sendButtonState = SendButtonState.idle;
+          desktopMuted = false;
         }
       });
 
@@ -423,6 +432,23 @@ class _InputSyncPageState extends State<InputSyncPage>
     }
   }
 
+  Future<void> _toggleMute() async {
+    if (!connection.connected) {
+      return;
+    }
+    final nextMuted = !desktopMuted;
+    setState(() {
+      desktopMuted = nextMuted;
+    });
+    final sent = await api.sendMute(nextMuted);
+    if (!sent && mounted) {
+      setState(() {
+        desktopMuted = !nextMuted;
+      });
+      _showToast('发送失败，连接已断开');
+    }
+  }
+
   Future<void> _saveHistory(String text) async {
     final trimmed = text.trim();
     if (trimmed.isEmpty) {
@@ -904,6 +930,13 @@ class _InputSyncPageState extends State<InputSyncPage>
                               icon: const Icon(Icons.delete_outline),
                             ),
                     ),
+                    IconButton(
+                      tooltip: desktopMuted ? '取消静音' : '静音桌面',
+                      onPressed: connection.connected ? _toggleMute : null,
+                      icon: Icon(
+                        desktopMuted ? Icons.volume_off : Icons.volume_up,
+                      ),
+                    ),
                   ],
                 ),
               ),