## What changed
- Add `RecoverTurnRequest` and `CodexThread::recover_turn_if_idle` to resume an interrupted regular turn with its existing turn ID and updated thread settings.
- Treat recovery separately from automatic idle work so it can resume in Plan mode without injecting an empty user message.
- Reject recovery while another turn is active without applying settings or queuing input.
## Testing
- Cover successful Plan-mode recovery, turn ID preservation, and the absence of an empty user message.
- Cover active-turn rejection and verify that it leaves settings and pending input unchanged.
GitOrigin-RevId: 2376fdc78b5d48b571633981960741ba269ab1ef