fix: remote video not showing — Room ChangeNotifier not listened to

_RemoteVideoView and _LocalVideoPip watched the Riverpod provider but
not the LiveKit Room's ChangeNotifier. When a remote participant joined
or published a track, notifyListeners() fired but no widget rebuilt.

Fix: wrap both views in ListenableBuilder(listenable: room) so they
rebuild on every Room event (participant connect, track subscribe, etc).

Added _AudioOnlyPlaceholder for when remote has audio but no video.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/features/calls/presentation/call_screen.dart

@@ -1,4 +1,4 @@
-// Version: 1.2.1 | Created: 2026-04-01 | Updated: 2026-04-03
+// Version: 1.3.0 | Created: 2026-04-01 | Updated: 2026-04-03
 // Full call screen with LiveKit video/audio.
 // - Remote video: full screen background
 // - Local video: picture-in-picture overlay (bottom right)
@@ -107,6 +107,8 @@ class _CallScreenState extends ConsumerState<CallScreen> {
 // Remote video view
 // ---------------------------------------------------------------------------
 
+/// Listens to the LiveKit Room's ChangeNotifier so it rebuilds when
+/// remote participants join/leave or publish/unpublish tracks.
 class _RemoteVideoView extends ConsumerWidget {
   const _RemoteVideoView();
 
@@ -117,24 +119,29 @@ class _RemoteVideoView extends ConsumerWidget {
       return const _NoVideoPlaceholder();
     }
 
+    // Room extends ChangeNotifier — rebuilds on every participant/track event.
+    return ListenableBuilder(
+      listenable: room,
+      builder: (context, _) {
         final remoteParticipants = room.remoteParticipants.values.toList();
         if (remoteParticipants.isEmpty) {
           return const _NoVideoPlaceholder();
         }
 
-    // Show the first remote participant's first video track.
         final firstParticipant = remoteParticipants.first;
         final videoPubs = firstParticipant.videoTrackPublications;
         if (videoPubs.isEmpty || videoPubs.first.track == null) {
-      return const _NoVideoPlaceholder();
+          // Participant joined but no video track yet — show audio indicator.
+          return _AudioOnlyPlaceholder(name: firstParticipant.identity);
         }
 
-    // safe: checked non-null above
         final videoTrack = videoPubs.first.track!;
         return VideoTrackRenderer(
           videoTrack,
           fit: RTCVideoViewObjectFit.RTCVideoViewObjectFitCover,
         );
+      },
+    );
   }
 }
 
@@ -148,7 +155,12 @@ class _LocalVideoPip extends ConsumerWidget {
   @override
   Widget build(BuildContext context, WidgetRef ref) {
     final room = ref.watch(liveKitServiceProvider).activeRoom;
-    final local = room?.localParticipant;
+    if (room == null) return const SizedBox.shrink();
+
+    return ListenableBuilder(
+      listenable: room,
+      builder: (context, _) {
+        final local = room.localParticipant;
         if (local == null) return const SizedBox.shrink();
 
         final videoPubs = local.videoTrackPublications;
@@ -156,7 +168,6 @@ class _LocalVideoPip extends ConsumerWidget {
           return const SizedBox.shrink();
         }
 
-    // safe: checked non-null above
         final localTrack = videoPubs.first.track!;
         return Positioned(
           right: 16,
@@ -175,6 +186,8 @@ class _LocalVideoPip extends ConsumerWidget {
             ),
           ),
         );
+      },
+    );
   }
 }
 
@@ -182,6 +195,39 @@ class _LocalVideoPip extends ConsumerWidget {
 // Placeholders and overlays
 // ---------------------------------------------------------------------------
 
+class _AudioOnlyPlaceholder extends StatelessWidget {
+  const _AudioOnlyPlaceholder({required this.name});
+  final String name;
+
+  @override
+  Widget build(BuildContext context) {
+    final initials = name.isNotEmpty ? name[0].toUpperCase() : '?';
+    return Container(
+      color: const Color(0xFF1A1A2E),
+      child: Center(
+        child: Column(
+          mainAxisAlignment: MainAxisAlignment.center,
+          children: [
+            CircleAvatar(
+              radius: 48,
+              backgroundColor: const Color(0xFF5C35C9),
+              child: Text(initials,
+                  style: const TextStyle(fontSize: 36, color: Colors.white)),
+            ),
+            const SizedBox(height: 16),
+            Text(name,
+                style: const TextStyle(color: Colors.white, fontSize: 18)),
+            const SizedBox(height: 8),
+            Text('Audio only',
+                style: TextStyle(
+                    color: Colors.white.withAlpha(153), fontSize: 14)),
+          ],
+        ),
+      ),
+    );
+  }
+}
+
 class _NoVideoPlaceholder extends StatelessWidget {
   const _NoVideoPlaceholder();