Mirrors the Gemini Live local-VAD example for OpenAI Realtime, showing
that `wait_for_transcript_to_end_user_turn=False` composes cleanly
with `turn_detection=False`. The OpenAI Realtime service already wires
`UserStoppedSpeakingFrame` to `input_audio_buffer.commit` +
`response.create` when `turn_detection=False`, so the example is the
only new code needed.
638294c1cc