Control Baton

A named group whose status is a sentence — who has control, and why when the agent asked for help — never the colour of the presence dot alone. Outside an AgentSurface the status line is itself a polite live region present from first paint; inside one it is not, since the surface already announces the change and two regions would say it twice. There is one action button whose label and purpose follow the holder, so focus stays on it as control changes. Hand back… opens a labelled note field and moves focus into it; Ctrl/⌘+Enter hands back, Escape cancels, and either returns focus to the button. If control moves elsewhere while the note is open, the note closes and focus returns to the button rather than falling to the page. The baton is marked data-agent-ui, so using it never counts as taking over by input.