Move world-building into `Greenhouse.from_config(cfg)`. Support custom node list from YAML; fall back to auto-grid. **Acceptance criteria:** - [ ] `Greenhouse.from_config(cfg)` classmethod; custom nodes from YAML; tests for both paths
Move world-building into
Greenhouse.from_config(cfg). Support custom node list from YAML; fall back to auto-grid.Acceptance criteria:
Greenhouse.from_config(cfg)classmethod; custom nodes from YAML; tests for both paths