Fix C3dMapper.__eq__() early return skipping remaining keys

[yasumorishima]

Summary

Closes #383

Fixes two early-return bugs in C3dMapper.__eq__() that caused the comparison to stop after checking only the first key, instead of iterating through all keys.

Changes

Bug 1: C3dMapper comparison (line 58)

# Before (bug): returns after comparing only the first child
return self._storage[key] == other._storage[key]

# After (fix): only return on mismatch, continue loop otherwise
if not (self._storage[key] == other._storage[key]):
    return False

Bug 2: numpy array comparison (line 62-67)

# Before (bug): returns True after the first matching array
np.testing.assert_array_equal(self._storage[key], other._storage[key])
return True

# After (fix): only return on mismatch, using simpler np.array_equal
if not np.array_equal(self._storage[key], other._storage[key]):
    return False

Bug 3: __eq_param__ numpy array handling (line 106-108)

The fix to Bug 1 & 2 causes meta_points (a dict containing numpy arrays like residuals and camera_masks) to be properly reached and compared. The existing else branch in __eq_param__ used dict1[key] != dict2[key], which raises ValueError for numpy arrays. Fixed by adding an np.array_equal check for numpy array values.

Tests

Added test_eq() with 5 assertions:

• Empty c3d objects are equal
• Populated c3d objects with identical data are equal
• Deepcopy is equal to original
• Modifying only analogs (not points) makes them unequal — this was the core bug: previously returned True
• Modifying only parameters (not header) makes them unequal — same bug at top level

Note on test_parse_and_rebuild failures

Some existing test_parse_and_rebuild and test_parse_and_rebuild_data tests now fail for certain formats (BTS, Optotrak, Vicon, Label2). This is not caused by this PR — it is a pre-existing issue that was masked by the broken __eq__. The old __eq__ returned True after comparing only the first key (points), so the write-read roundtrip data loss in other keys (meta_points, analogs, etc.) was never detected. The header and parameters comparisons continue to pass for all formats.

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This change is 

[pariterre]

@pariterre reviewed 2 files and all commit messages, and made 1 comment.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @yasumorishima).

[pariterre]

@yasumorishima
Thanks for spotting and correcting this error. I reckon the tests will predictably fails, so no bother! I am currently in vacation, so I'll accept the PR as is, and fix the tests when I come back to work :)

[yasumorishima]

Thank you for the review and approval! No rush at all — enjoy your vacation. I'm happy to help with anything when you're back.