Requested baton PV TimeoutError when handing back baton during scheduled shutdown

The below event occurred during completion of UDC prior to a scheduled shutdown.

https://graylog.diamond.ac.uk/search?streams=66264f5519ccca6d1c9e4e03&rangetype=absolute&q=&from=2026-06-23T07%3A46%3A02.981789%2B00%3A00&to=2026-06-23T07%3A51%3A03.981789%2B00%3A00

It seems that the put to the requested user baton PV timed out / was cancelled after completing robot unload.

Since we previously already made this put to the requested user PV to exit the collection loop, perhaps the timeout was due to the PV already having the expected value. This seems odd behaviour - although strictly speaking we don't need to do two puts - we could just exit the loop normally and this may be a possible fix.

## Acceptance Criteria
- Baton is successfully handed back when the countdown timeout is below threshold.

Start with the linked Graylog event and trace the requested-user baton handback during scheduled shutdown and the countdown timeout path. Confirm the behavior when the requested-user PV already has the expected value, then verify the acceptance criterion by exercising a handback with the countdown below threshold.

Written by the indexing model from the issue text.