The chat UI — message list, composer, attachments and the streaming turn view, as UiNode-rendering components and the controllers that serve them. A library, like mc-agent-api-rest: no Spring Boot main class, so a host app decides how it is wired and secured. This is the lower of the two UI modules: the admin UI depends on it for its own chat page, not the other way round. A user-facing chat must not have to ship agent CRUD, LLM configs, traces ...