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/linux/runner/main.cc

@@ -1,6 +1,16 @@
+#include <stdio.h>
+#include <unistd.h>
+
 #include "my_application.h"
 
 int main(int argc, char** argv) {
-  g_autoptr(MyApplication) app = my_application_new();
-  return g_application_run(G_APPLICATION(app), argc, argv);
+  MyApplication* app = my_application_new();
+  int status = g_application_run(G_APPLICATION(app), argc, argv);
+  // The window is gone and the engine with it (the app disposed its mpv
+  // players and left before closing the window). Skip exit(): its handlers
+  // include NVIDIA's EGL teardown (libEGL_nvidia), which segfaults inside
+  // exit() for Flutter apps. Nothing is left to flush but stdio.
+  fflush(stdout);
+  fflush(stderr);
+  _exit(status);
 }

apps/desktop/linux/runner/my_application.cc

@@ -1,5 +1,8 @@
 #include "my_application.h"
 
+#include <stdio.h>
+#include <unistd.h>
+
 #include <flutter_linux/flutter_linux.h>
 #ifdef GDK_WINDOWING_X11
 #include <gdk/gdkx.h>
@@ -38,6 +41,28 @@ static void window_method_cb(FlMethodChannel* channel, FlMethodCall* call,
   fl_method_call_respond(call, response, nullptr);
 }
 
+// Ends the process 15 s after the first close request whatever is still
+// running: the app's close (lib/src/platform/app_shutdown.dart) is bounded
+// to a few seconds, but a native teardown can block for good, and the
+// process must never stay behind a hidden window.
+static gpointer exit_watchdog(gpointer data) {
+  g_usleep(15 * G_USEC_PER_SEC);
+  fflush(stdout);
+  fflush(stderr);
+  _exit(0);
+  return nullptr;
+}
+
+static gboolean window_delete_cb(GtkWidget* widget, GdkEvent* event,
+                                 gpointer user_data) {
+  static gboolean armed = FALSE;
+  if (!armed) {
+    armed = TRUE;
+    g_thread_unref(g_thread_new("exit-watchdog", exit_watchdog, nullptr));
+  }
+  return FALSE;  // window_manager decides whether the window closes
+}
+
 static gboolean window_focus_in_cb(GtkWidget* widget, GdkEvent* event,
                                    gpointer user_data) {
   gtk_window_set_urgency_hint(GTK_WINDOW(widget), FALSE);
@@ -111,6 +136,10 @@ static void my_application_activate(GApplication* application) {
                            self);
   gtk_widget_realize(GTK_WIDGET(view));
 
+  // Before the plugins: window_manager's delete-event handler stops the
+  // emission while the app holds the close.
+  g_signal_connect(window, "delete-event", G_CALLBACK(window_delete_cb),
+                   nullptr);
   fl_register_plugins(FL_PLUGIN_REGISTRY(view));
 
   g_autoptr(FlStandardMethodCodec) codec = fl_standard_method_codec_new();