Built-in role agent that uses workflow config models directly,
with its own tool-calling run loop. No external agent dependency.
- OpenAI-compatible chat completion client with tool_calls support
- P0 toolkit: read_file, write_file, run_command
- Integrates via createAgent factory from workflow-agent-kit
- CAS detail recording for each turn
- Path sandboxing and shell opt-in (UWF_BUILTIN_ALLOW_SHELL)
