## Depth Data Saving Integration
- Integrated `--save-depth` flag into `calibrate_extrinsics.py`.
- Uses `aruco.depth_save.save_depth_data` to persist HDF5 files.
- Captures:
  - Intrinsics and resolution.
  - Pooled depth and confidence maps.
  - Pool metadata (RMSE comparison, fallback reasons).
  - Raw candidate frames (depth, confidence, score, frame index).
- Logic is guarded: only runs if `verify_depth` or `refine_depth` is enabled.
- Added integration test `tests/test_depth_save_integration.py` using mocks to verify data flow without writing actual HDF5 files during testing.