Add raw ArUco marker detection and preserve in frame output
Refactor ArUco detection to expose raw marker data (IDs and corners)
alongside the computed bounding polygon. Frame JSONL output now includes
an "aruco" field with detected markers and masked status.
- Add detect_markers() returning raw {markers, polygon} dict
- Remove detect_convey_region() wrapper (unused after refactor)
- Thread aruco metadata through VideoProcessor to JSONL output
- Update mask_convey_region() docstring
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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>