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/lib/src/screens/home/ui.dart

@@ -22,6 +22,10 @@ String displayVersion({String version = appVersion, String pubspec = _pubspecVer
   return isDevBuild(version) && commit.isNotEmpty ? '$version · $commit' : version;
 }
 
+/// The version in a few characters, always on screen (under the strip's
+/// Settings tab): "1.2.1", "1.2.1-dev.2", "dev run".
+String shortVersion({String version = appVersion}) => version == '0.0.0-dev' ? 'dev run' : version;
+
 const kRadius = 12.0;
 const kGap = 16.0;