EventController.#handleAgentEnd guarded only on session.isStreaming, so a
non-terminal agent_end (isTerminal:false, emitted while an async job will
re-wake the loop) flipped the terminal title to idle and tore down the
working loader while a /vibe worker or async bash job was still running.
Early-return on event.isTerminal === false, matching the guard every other
agent_end consumer already applies; the later terminal agent_end performs
the normal teardown.
Fixes#7386
roboomp
4e4c5564c9