The retry branch is only reachable via `except Exception`, and
`CancelledError` inherits from `BaseException`, so today it naturally
bypasses the retry path and /stop still works. Add one focused
regression test so any future refactor that widens the retry catch to
`BaseException`, re-orders the handlers, or adds `CancelledError` to
`_TRANSIENT_EXC_NAMES` fails CI instead of silently swallowing /stop.
Made-with: Cursor