Adds bounded retry/backoff around LocalFileStreamProvider.Replace to handle transient File.Replace failures on Windows - #174

Summary

Adds bounded retry/backoff around LocalFileStreamProvider.Replace to handle transient File.Replace failures on Windows, such as watcher-related interference from tools like editors or file indexers.

The implementation preserves ZoneTree’s existing atomic replacement behavior by continuing to use File.Replace; it only retries transient IOExceptions before surfacing the original failure.

Changes

• Retry File.Replace on retryable IOExceptions with short bounded backoff delays: 10ms, 25ms, 50ms, 100ms, 200ms.
• Avoid retries for structural path/file errors such as:
  • FileNotFoundException
  • DirectoryNotFoundException
  • DriveNotFoundException
  • PathTooLongException
• Add deterministic unit tests for:
  • eventual success after transient failures
  • rethrow after retry exhaustion
  • no retry for missing source file

Motivation

On Windows, File.Replace may fail transiently with errors like “Unable to remove the file to be replaced” when another process has a FileSystemWatcher active on the directory. Retrying briefly handles that interference without replacing the atomic operation with a less durable delete/move fallback.