adds buffering intermediate state

Co-authored-by: Copilot <copilot@github.com>

lib/main.dart

@@ -58,6 +58,17 @@ class _MainPageState extends State<MainPage> {
   StreamingAudioBusinessObject get _audio => widget.audio;
   late final WebViewController _webViewController;
 
+  String _playbackStatusLabel() {
+    switch (_audio.playbackStatus) {
+      case StreamingPlaybackStatus.stopped:
+        return 'Stopped';
+      case StreamingPlaybackStatus.buffering:
+        return 'Buffering...';
+      case StreamingPlaybackStatus.playing:
+        return 'Playing';
+    }
+  }
+
   @override
   void initState() {
     super.initState();
@@ -193,17 +204,17 @@ class _MainPageState extends State<MainPage> {
                     mainAxisAlignment: MainAxisAlignment.center,
                     children: [
                       ElevatedButton(
-                        onPressed: _audio.isPlaying ? null : _play,
+                        onPressed: _audio.isStopped ? _play : null,
                         child: const Text('▶️'),
                       ),
                       const SizedBox(width: 12),
                       ElevatedButton(
-                        onPressed: _audio.isPlaying ? _stop : null,
+                        onPressed: _audio.isStopped ? null : _stop,
                         child: const Text('⏹️'),
                       ),
                       const SizedBox(width: 16),
                       Text(
-                        _audio.isPlaying ? 'Playing' : 'Stopped',
+                        _playbackStatusLabel(),
                         style: TextStyle(color: themeColors.statusText),
                       ),
                     ],