Exclude Lock Files from Synchronization

[i2h3]

For the special use case of the sever not supporting locks.

[Copilot]

Pull Request Overview

This PR updates the error handling for lock files when server-side locking capabilities are unavailable. Instead of returning a generic synchronization error, the code now uses the more appropriate excludedFromSync error on macOS 13.0+, while maintaining backward compatibility with earlier versions. The change includes improved logging to clarify why lock files are being excluded.

• Returns NSFileProviderError(.excludedFromSync) on macOS 13.0+ when locking capability is missing
• Maintains backward compatibility by using cannotSynchronize error on earlier macOS versions
• Adds debug logging to explain why lock files are excluded from synchronization

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