🧪 Add tests for os.fchmod fallback logic in _owner_only_opener

[google-labs-jules]

🎯 What: The testing gap for the fallback exception handling in utils._owner_only_opener was addressed. Specifically, when os.fchmod raises an AttributeError (e.g., missing on Windows) or OSError (e.g., failure on an exotic file system), the exceptions are now fully tested.
📊 Coverage: Two test scenarios were added to tests/test_utils.py:

1. test_owner_only_opener_fchmod_attributeerror: Mocks the absence of os.fchmod to trigger the AttributeError fallback path.
2. test_owner_only_opener_fchmod_oserror: Mocks an implementation of os.fchmod that raises an OSError to cover the system error fallback path.
   ✨ Result: Test coverage for hooks/utils.py has improved to 100%. The system correctly bypasses errors in the _owner_only_opener flow and returns a valid file descriptor as expected.

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PR created automatically by Jules for task 16418241831103222766 started by @zknpr

[google-labs-jules]

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