Realtime: enable a playback tracker

[rm-openai]

So far, we've been assuming that audio is played:

• immediately (i.e. with 0 delay/latency)
• at realtime

This causes issues with our interrupt tracking. The model wants to know how much audio the user has actually heard. For example in a phone call agent, this wouldn't work (bc theres a delay of a few hundred ms between model sending audio and the user hearing it). This PR allows you to pass a playback tracker.

---

• Realtime: forward all raw model events #1252
• Realtime: Twilio example #1216
• Realtime: only cancel response if necessary #1243
• -> Realtime: enable a playback tracker #1242

[seratch]

it seems the file conflicts with main branch need to be resolved

[seratch]

minor suggestion of naming local variables; they are local variables so it's okay to use the same name though

[seratch]

nit: In general, using built-in/reserved names like bytes for variables should be avoided. If audio does not sound great, data, delta, audio_data etc. should be fine too.

Suggested change

	def on_audio_delta(self, item_id: str, item_content_index: int, bytes: bytes) -> None:
	"""Called when an audio delta is received from the model."""
	ms = calculate_audio_length_ms(self._format, bytes)
	new_key = (item_id, item_content_index)
	self._last_audio_item = new_key
	if new_key not in self._states:
	self._states[new_key] = ModelAudioState(datetime.now(), ms)
	else:
	self._states[new_key].audio_length_ms += ms
	def on_audio_delta(self, item_id: str, item_content_index: int, audio: bytes) -> None:
	"""Called when an audio delta is received from the model."""
	ms = calculate_audio_length_ms(self._format, audio)
	new_key = (item_id, item_content_index)
	self._last_audio_item = new_key
	if new_key not in self._states:
	self._states[new_key] = ModelAudioState(datetime.now(), ms)
	else:
	self._states[new_key].audio_length_ms += ms

[seratch]

same as above

Suggested change

	def calculate_audio_length_ms(format: RealtimeAudioFormat | None, bytes: bytes) -> float:
	if format and format.startswith("g711"):
	return (len(bytes) / 8000) * 1000
	return (len(bytes) / 24 / 2) * 1000
	def calculate_audio_length_ms(format: RealtimeAudioFormat | None, audio: bytes) -> float:
	if format and format.startswith("g711"):
	return (len(audio) / 8000) * 1000
	return (len(audio) / 24 / 2) * 1000