Sync from internal repo (2026/07/22)

[ccampbell-aai]

4.36.4

• Add aac to the streaming encoding options — accepts an AAC stream in ADTS framing. Like opus/ogg_opus, AAC is self-describing, so sampleRate is optional for it (it remains required for PCM encodings and for dual-channel mode)
• Add opt-in sessionHeartbeat streaming param — when enabled, the server emits a periodic Heartbeat message, surfaced via the new heartbeat event with total_audio_received_ms, total_duration_ms, realtime_factor, and max_speech_probability. Requires the universal-3-5-pro streaming model