Expands the stub openapi.yaml into a complete Interface Control Document
covering every kernel HTTP endpoint. 22 tag groups, 15 reusable component
schemas, inline request/response definitions for all routes. Served at
/api/docs (Swagger UI) and /api/docs/openapi.yaml.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>