fix: handle permission errors gracefully when writing package-lock.yml

[claygeo]

Fixes #9241.

dbt deps fails with an unhandled PermissionError when run in a read-only directory (common in container environments with mounted project volumes). The lock() method tries to write package-lock.yml via open(lock_filepath, 'w'), which raises PermissionError; dbt exits with no output and no packages installed.

Fix

Wrap the lock-file write in a try/except OSError (which covers PermissionError, FileNotFoundError, etc.). On failure, fire a WARN-level log message and proceed — packages continue to install normally using packages.yml.

The warning is fired at EventLevel.WARN (not INFO) so it stands out in the console and structured log consumers can route it correctly.

Before: (silence — no packages installed, cryptic exit)

After:  [WARN] Could not write lock file at /project/package-lock.yml:
        [Errno 13] Permission denied. Proceeding without updating the lock file.
        ... (packages install normally)

The rest of dbt deps still works because load_yml_dict returns {} for missing files and the resolver falls back to packages.yml.

Checklist

• My code follows the dbt coding conventions
• I have signed the CLA
• I have run this code in development and it appears to work correctly
• I have added a changie entry

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