perf: parallelize pose + object detection and reduce throttle frequency
Run pose detection on a dedicated thread concurrently with object
detection so per-frame latency is max(pose, object) instead of the
sum. Also bump detection throttle from 20ms (~50 FPS) to 33ms (~30 FPS)
to reduce CPU contention with minimal perceptual difference.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>