chore: consolidate development changes and refactor agent system

Major Changes:
- Rename codebase-agent to opencoder for clarity
- Add agent validator plugin with comprehensive testing
- Refactor prompt engineering commands (enhancer → optimizer)
- Update task-manager subagent with improved workflows
- Enhance plugin system with validation and documentation

Agent System:
- Renamed: codebase-agent.md → opencoder.md
- Updated: task-manager.md with better delegation patterns
- Added: opencoder.md documentation

Plugin System:
- New: agent-validator.ts for prompt validation
- New: VALIDATOR_GUIDE.md with usage instructions
- New: Test suite (test-validator.sh, test-validation.sh)
- Updated: notify.ts, telegram-notify.ts with improvements
- Updated: package.json, bun.lock with new dependencies

Commands:
- Renamed: prompt-enchancer.md → prompt-engineering/prompt-enhancer.md
- New: prompt-engineering/prompt-optimizer.md
- Updated: build-context-system.md, validate-repo.md

Documentation:
- Updated: README.md with latest features
- Updated: openagent.md documentation
- New: opencoder.md agent documentation
- Updated: agent-system-blueprint.md
- Updated: system-builder docs (README, quick-start)
- Updated: installation.md, collision-handling.md

Registry:
- Updated: registry.json with new components

This consolidates all development work for the upcoming release.