style: apply dart formatting fixes across lib/ and test/

11 files had formatting inconsistencies that caused the
--set-exit-if-changed gate to fail. Automated formatting
via dart format now passes cleanly.

lib/main.dart

@@ -139,7 +139,7 @@ class _MainPageState extends State<MainPage> with WidgetsBindingObserver {
     _liveInfo.addListener(_handleLiveInfoChanged);
     _liveInfo.start();
     _playbackChannel.setMethodCallHandler(_handlePlaybackMethodCall);
-    
+
     // When native code requests local audio to stop (cast media loaded)
     _casting.onStopLocalAudioRequested = () {
       unawaited(_audio.stop());
@@ -458,8 +458,7 @@ class _MainPageState extends State<MainPage> with WidgetsBindingObserver {
                         label: const Text('Stop'),
                       ),
                       ElevatedButton.icon(
-                        onPressed:
-                            _casting.status == CastingStatus.connecting
+                        onPressed: _casting.status == CastingStatus.connecting
                             ? null
                             : _toggleCasting,
                         icon: Icon(_castingIcon()),