task.cancel() can't preempt the run_in_executor thread running
run_conversation(), so we rely on agent.interrupt() to wake the loop.
Without a timeout, a slow/unresponsive interrupt blocks the HTTP
response indefinitely. Wrap the await in wait_for(shield(task), 5.0)
and log a warning on timeout.
Also tidy one extra space in the module docstring's /stop entry.