v1.4.2 — screenshots no longer hang

• Screenshot capture is bounded: ScreenCaptureKit lookup times out after 5s and image capture after 10s, so a wedged capture service can no longer hold the per-app lock and freeze later mac-use calls.
• Faster screenshots: the window lookup lists only on-screen windows (about 2x faster end-to-end in local tests: ~0.3s vs ~0.65s per screenshot).