feat: add MAINTAINING.md #20

Description

Add MAINTAINING.md with comprehensive operational documentation for maintainers.

Acceptance Criteria

• MAINTAINING.md created at repo root
• Tool Boundary table (Peribolos vs safe-settings ownership)
• Common Workflows: add/remove members, create teams, add repos, change branch protection
• Override Validator Policies documentation
• Local Validation commands
• Applying Changes section (safe-settings sync, peribolos apply)
• Troubleshooting section
• Adapted for unbound-force org (8 code repos: containerfile, dewey, gaze, homebrew-tap, intake-kit, replicator, unbound-force, website)

References

• Modeled on: zero-dot-force/.github/MAINTAINING.md