Add HandRunner for executing Hands:
- hands/runner.py: Hand execution engine
- Load SYSTEM.md and SKILL.md files
- Inject domain expertise into LLM context
- Check and handle approval gates
- Execute tool loop with LLM
- Deliver output to dashboard/channel/file
- Log execution records
- hands/__init__.py: Module exports
- Export all public classes and models
- Usage documentation
The HandRunner completes the core Hands infrastructure.