PR #23458 introduced _send_message_with_thread_fallback() and applied it
to all control-style sends (send_update_prompt, send_approval_request,
send_model_picker_prompt), but the slash-confirm result message in
handle_callback_query still called self._bot.send_message directly.
In supergroups with stale message_thread_id on the callback's parent
message, this raises "Message thread not found" and silently swallows
the result text. Replace with the helper so the same retry-without-
thread-id logic applies.
e474130c48