Consume the durable message-feedback sidecar from #2217 in the browser:
per-message Like/Dislike with an optional note, contributed through a
declared assistant-actions slot.
- carry MessageId on finalized AssistantMessageNode so a target is nameable
- declare conversation.chat.assistant-actions and render it in the
IconActions row between copy and branch
- hold one FeedbackController per Session with per-item ifVersion CAS,
reconciling a version-conflict from the reply's authoritative item
- mount messageFeedbackRemote alongside goalsRemote
Master added this scenario while this branch was open, so its golden froze
the composer seat's "Select model" fallback. The scaffold's route-only
adapter (added here for fixture-less scenarios) makes the seat resolve the
model those scenarios actually route to, which is what the other eight
goldens on this branch already show. Only the two seat lines move.
