A person's word is heard once even when steering a running agent fails #827

Pillar: P7 Steering, under #593. Found while building #807.

When a person comments while an agent's run is in flight, the forge tries to steer the words into that run. When steering fails (the session is not reachable yet, or it is winding down), a follow-up run is queued instead. The follow-up's news starts when the in-flight run ended, and the person's comment is older than that. So the comment was never in the in-flight run's brief, and it is not in the follow-up's either. Before #807 the follow-up declined ("no feedback to act on"). Since #807 it is skipped. Either way, the person's words are never acted on.

Done means:

• [ ] Words a person said while a run was in flight are heard exactly once. Either the forge records which words were steered into a run, or a failed steer moves the follow-up's since back to cover them.
• [ ] A test: a comment whose steer fails reaches the next run's brief, and a comment that was steered does not reach it again.

Narrowed now that #819 has landed. A follow-up now reads what was said since its agent's last ended run began (crew/news.ts feedbackSince), so a word that could not be steered into a running agent is no longer lost: the next run hears it.

What is left is exactly once: a word that was steered into a run is quoted again in the next follow-up's brief. Done means the forge records which words a run heard by steering, and the next brief leaves those out, with a test that a steered word is not quoted twice and an unsteered one is quoted once.