- Implement PersistentIdentity class for months/years persistence
- Store identities in ~/.ruvector/identities with encrypted backup
- Track contribution history in ~/.ruvector/contributions
- Add --list command to show all stored identities
- Add --history command to show contribution milestones
- Auto-restore identities across sessions
- Track "return after absence" milestones (>30 days)
- Session tracking with timestamps
- Add multi-contributor-test.js for network simulation
- All contributions preserved indefinitely
