reactor(ragfs): prevent recursive backup sync loop by moving default backup workspace and renaming config key

[baojun-zhang]

Description

fix local multi-write backup defaults and config naming for localfs backups to avoid recursive sync paths and align backup configuration with the existing workspace convention.

Related Issue

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactoring (no functional changes)
• Performance improvement
• Test update

Changes Made

• Changed the default localfs backup directory from /viking/_backups/ to /_backups/ so backup data is no longer placed under the primary local mount root.
• Renamed the user-facing local backup config field from local.local_dir to local.workspace , while still translating it to the internal localfs plugin param local_dir .
• Updated multi-write tests and user-facing docs/examples to use local.workspace and document the new local backup behavior.

Testing

• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have tested this on the following platforms:
  • Linux
  • macOS
  • Windows

Checklist

• My code follows the project's coding style
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published

Screenshots (if applicable)

Additional Notes