spwn agent create

Create a new agent with a SOUL.md at the agent root and the two Mind layer directories (playbooks/journal). Skills aren't a Mind layer — they're build-time dependencies resolved via the skill/ form or shipped by tools, injected into /world/skills/ at image time. Knowledge is world-scoped, not agent-scoped — it lives at /world/knowledge/ when a world opts in via spwn.yaml's worlds.<name>.knowledge key, which resolves to a host path under the project root. If no name is provided, a random name is picked from a curated dictionary. With --force, an existing agent's Mind is re-scaffolded: any missing files are recreated and the command exits zero even if the agent already exists.