Stabilisation quick fixes: orderly close, visible version and update band, chat pop-ups on, Windows shaders and hwdec, render logs

- Close: hide the window, dispose every player, thumbnail job and the
  sound engine, leave, then close normally; Linux runner _exit (the
  NVIDIA EGL exit handler crashed 10/10 closes, 0/41 now); Windows tears
  down inside the message loop, then TerminateProcess; watchdogs.
- Version under the Settings tab; an update band instead of a dot,
  never over a video; checks at start and every 4 hours.
- Chat pop-ups default to All again.
- Shader read-back compared as a list (old mpv joins with ','), so
  Windows stops turning shaders off; Windows hwdec auto-copy.
- Render diagnostics (`mpv: render` lines); RAM-only demuxer cache pin
  silences the file-cache warning; a volume readout test.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/desktop/test/shell_test.dart

@@ -68,14 +68,14 @@ void main() {
     coord.toasts.value = [];
   });
 
-  Future<void> pumpShell(WidgetTester tester, Size size) async {
+  Future<void> pumpShell(WidgetTester tester, Size size, {UpdateController? updates}) async {
     tester.view.physicalSize = size;
     tester.view.devicePixelRatio = 1;
     addTearDown(tester.view.reset);
     await tester.pumpWidget(MaterialApp(
       theme: ThemeData.dark(),
       home: AppShell(
-        updates: UpdateController(currentVersion: '0.0.0-dev'),
+        updates: updates ?? UpdateController(currentVersion: '0.0.0-dev'),
         autoUpdateCheck: false,
         windowControls: false,
         videoBuilder: (context, controls) => const FakeVideo(),
@@ -93,6 +93,36 @@ void main() {
     member('f', 'Finn'),
   ];
 
+  group('version and update bar', () {
+    testWidgets('the version under Settings; the bar on the tabs, off the full player until the video ends',
+        (tester) async {
+      final updates = UpdateController(currentVersion: '0.0.0-dev');
+      await pumpShell(tester, const Size(1280, 800), updates: updates);
+      expect(find.text('dev run'), findsOneWidget);
+      expect(find.byKey(const ValueKey('update-bar')), findsNothing);
+      updates.status.value = const UpdateStatus(UpdatePhase.available,
+          manifest: UpdateManifest(version: '9.9.9', protocol: 1, url: 'http://x/a.tgz', notes: ''),
+          canInstall: true);
+      await tester.pumpAndSettle();
+      expect(find.byKey(const ValueKey('update-bar')), findsOneWidget);
+      online(party);
+      await tester.pumpAndSettle();
+      expect(find.byKey(const ValueKey('update-bar')), findsNothing);
+      final r = coord.serverState.value!;
+      coord.serverState.value = StateBroadcast(
+        eventId: 2,
+        transport: 'finished',
+        position: 0,
+        serverTime: r.serverTime,
+        mediaId: r.mediaId,
+        media: r.media,
+        members: r.members,
+      );
+      await tester.pumpAndSettle();
+      expect(find.byKey(const ValueKey('update-bar')), findsOneWidget);
+    });
+  });
+
   group('party strip', () {
     testWidgets('offline: Join and Host, no party', (tester) async {
       await pumpShell(tester, const Size(1280, 800));