- Add optional 'nomad' extra (aiohttp)
- Add tools/nomad_slotpool.py: minimal Nomad client + slot pool + sync thread wrapper
- Add tools/sandbox_server.py + tools/sandbox/Dockerfile for sandbox container image
- Extend terminal_tool to support TERMINAL_ENV=nomad (acquire slot per task_id)
- Document draft usage in README and add nomad-dev.hcl
NOTE: Not tested on cluster; intended for later live validation.
