Upgrade already applied via mise/pipx. Key upstream changes:
- Borg warnings handling improved (file-not-found reverted to warning in 2.1.3)
- Memory and performance improvements in pre-backup validation
- source_directories_must_exist default now true (already set in our config)
Dry-run verified against both sifaka and borgbase repositories.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
