feat: add threading to Scheduler, fix desktop background selection freeze issue

programs/src/desktop/main.cpp

@@ -684,6 +684,12 @@ void gui::desktop_run(DesktopState* ds) {
         uint64_t now = montauk::get_milliseconds();
         sceneChanged |= desktop_refresh_panel_state(ds, now);
 
+        // Pick up any wallpaper buffer produced by a background loader.
+        if (wallpaper_poll(&ds->settings)) {
+            desktop_mark_background_dirty(ds);
+            sceneChanged = true;
+        }
+
         uint64_t launcherBlinkToken = desktop_launcher_blink_token(ds, now);
         if (launcherBlinkToken != lastLauncherBlinkToken) {
             lastLauncherBlinkToken = launcherBlinkToken;