Under the hood
Rewind now reports a specific reason when it can't jump back to a point in a session
What
'Rewind' (jumping a session or prompt back to an earlier point) now has a defined set of named outcomes for why a rewind couldn't happen: commands_queued, prompt_pending, turn_running, target_not_found, stale_target, unseen_later_turn, poll_tool_result_target, delivered_poll_events_in_range, persist_failed, and state_changed. Each maps to a human-readable explanation, and a helper always returns rewound: false along with the reason when a rewind fails.
Why
This gives clearer, more specific feedback about why a rewind attempt didn't succeed, instead of a generic failure, making it easier to understand what state the session was in that blocked it.