fix(overlay): identify Windows mpv windows through IPC PID (#330)

.github/workflows/quality-gate.yml

@@ -32,6 +32,9 @@ jobs:
       - name: Verify native mpv process launch
         run: bun test src/main/runtime/mpv-process.test.ts
 
+      - name: Verify mpv PID lookup and Windows tracker
+        run: bun test src/window-trackers/mpv-process-id.test.ts src/window-trackers/windows-tracker.test.ts
+
       - name: Verify POSIX launcher bootstrap
         run: bun test src/main/runtime/posix-launcher-bootstrap.test.ts