Cancel pending Linux MPV fullscreen overlay refresh bursts

- return a cancel handle from the Linux refresh burst scheduler
- clear pending refresh bursts when overlays hide or windows close
- tighten the burst test polling to wait for the async refresh

src/main/runtime/linux-mpv-fullscreen-overlay-refresh.test.ts

@@ -32,7 +32,10 @@ test('linux mpv fullscreen overlay refresh burst schedules overlay refresh work
       ensureOverlayWindowLevel: () => calls.push('ensureOverlayWindowLevel'),
     });
 
-    await new Promise((resolve) => setTimeout(resolve, 10));
+    const deadline = Date.now() + 200;
+    while (!calls.includes('updateVisibleOverlayVisibility') && Date.now() < deadline) {
+      await new Promise((resolve) => setTimeout(resolve, 5));
+    }
 
     assert.ok(calls.includes('updateVisibleOverlayVisibility'));
     assert.ok(calls.includes('hide'));

src/main/runtime/linux-mpv-fullscreen-overlay-refresh.ts

@@ -15,6 +15,7 @@ export type LinuxMpvFullscreenOverlayRefreshDeps = {
   };
   ensureOverlayWindowLevel: (window: LinuxMpvFullscreenOverlayWindow) => void;
 };
+export type CancelLinuxMpvFullscreenOverlayRefreshBurst = () => void;
 
 const LINUX_MPV_FULLSCREEN_OVERLAY_REFRESH_DELAYS_MS = [0, 50, 150, 300, 600] as const;
 let linuxMpvFullscreenOverlayRefreshTimeouts: Array<ReturnType<typeof setTimeout>> = [];
@@ -47,9 +48,9 @@ function refreshLinuxVisibleOverlayAfterMpvFullscreenChange(
 
 export function scheduleLinuxVisibleOverlayFullscreenRefreshBurst(
   deps: LinuxMpvFullscreenOverlayRefreshDeps,
-): void {
+): CancelLinuxMpvFullscreenOverlayRefreshBurst {
   if (process.platform !== 'linux') {
-    return;
+    return () => {};
   }
 
   clearLinuxMpvFullscreenOverlayRefreshTimeouts();
@@ -63,6 +64,7 @@ export function scheduleLinuxVisibleOverlayFullscreenRefreshBurst(
     refreshTimeout.unref?.();
     linuxMpvFullscreenOverlayRefreshTimeouts.push(refreshTimeout);
   }
+  return clearLinuxMpvFullscreenOverlayRefreshTimeouts;
 }
 
 export { clearLinuxMpvFullscreenOverlayRefreshTimeouts };