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/shaders/shader_presets.dart

@@ -85,3 +85,11 @@ String shaderListSeparator({bool? windows}) =>
 /// The `glsl-shaders` value for [paths].
 String joinShaderPaths(List<String> paths, {bool? windows}) =>
     paths.join(shaderListSeparator(windows: windows));
+
+/// Whether mpv's read-back [got] of `glsl-shaders` is the list [paths].
+/// Recent mpv prints a path list joined with [shaderListSeparator]; older
+/// mpv (0.37 and before, the bundled Windows libmpv among them) joins it
+/// with ','. Matched against each joined form rather than split: a path
+/// may itself hold ':' (a Windows drive letter) or ','.
+bool shaderListMatches(List<String> paths, String? got) =>
+    got != null && const [',', ';', ':'].any((sep) => paths.join(sep) == got);