[FR-7-03] AI quest authoring

[SamMRoberts]

ID: FR-7-03\nType: FR\nPhase: 7\nBaseline: false\n\nDescription\nGuardrails (reachability checks, no softlocks).\n\nAcceptance Criteria\n- [ ] Implemented\n- [ ] Tests passing\n- [ ] Docs updated