docs: update OpenAgent documentation and add repository validation

- Update OpenAgent docs with universal agent philosophy
- Change delegation criteria from 3+ to 4+ files
- Emphasize critical rules (approval gate, stop on failure, confirm cleanup)
- Create essential-patterns.md context file
- Add 11 context files to registry (standards/*, workflows/*)
- Create /validate-repo command for consistency checking
- Update all profile component counts (developer: 30, full: 36, advanced: 43)
- Ensure CLI compatibility with context file structure