- Set points.flags.writeable = False in HandsDetector.detect() so in-place
mutation of HandLandmarks.points raises ValueError (frozen=True alone does not
protect numpy array contents)
- Extend test_handlandmarks_is_immutable to assert ValueError on array mutation
- Add test_camera.py with 3 tests covering is_open, frames() yield/break
behaviour, and context manager release (was at 0% coverage)
- Remove unused `import numpy as np` from camera.py; fix frames() return
annotation to Iterator (np.ndarray ref removed with the import)
