2b86d71c1d
One speaker, two listeners A and B. Push 3 frames (both receive), A unsubscribes, push 3 more frames, B's stream completes with all 6. If A's unsubscribe accidentally tore down the speaker's broadcast or B's subscribe (e.g. an over-eager session-wide cleanup in a future refactor), B would time out waiting for the second batch — and the test names that exact failure mode in the message.