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/windows/runner/main.cpp

@@ -2,6 +2,8 @@
 #include <flutter/flutter_view_controller.h>
 #include <windows.h>
 
+#include <cstdio>
+
 #include "flutter_window.h"
 #include "utils.h"
 
@@ -38,6 +40,13 @@ int APIENTRY wWinMain(_In_ HINSTANCE instance, _In_opt_ HINSTANCE prev,
     ::DispatchMessage(&msg);
   }
 
+  // The window closed through WM_CLOSE (the app disposed its mpv players
+  // and left first), so the engine and plugins were torn down inside the
+  // loop. End here without the CRT exit and DLL_PROCESS_DETACH: a driver
+  // or libmpv detach handler can hang waiting on threads that are gone.
+  // Nothing is left to flush but stdio.
+  fflush(nullptr);
   ::CoUninitialize();
+  ::TerminateProcess(::GetCurrentProcess(), EXIT_SUCCESS);
   return EXIT_SUCCESS;
 }