These messages are developer instructions to the assistant (e.g. "Please
introduce yourself to the user"), not simulated user input. The
"developer" role is semantically correct for this purpose.
- Speechmatics: move config build after super().__init__ and settings
delta so turn_detection_mode (e.g. ADAPTIVE) takes effect
- Google STT: fix example passing bare Language enum instead of list
- Google TTS: add missing explicit defaults for all custom settings fields
- Soniox: fix accidental tuple wrapping of STT service in example
- Speechmatics examples: fix system->user role in kick-off messages
- Deepgram Flux: move tag from settings to __init__ (billing metadata)
- ElevenLabs STT: default tag_audio_events to None (use API default)
- Fal STT: simplify language default handling
- Google TTS: rename GoogleStreamTTSSettings to GoogleTTSSettings
Add `system_instruction` field to `LLMSettings` so it is runtime-updatable via settings.
For Google (GoogleLLMService, GoogleVertexLLMService), deprecate the init-time arg since it was already shipped. For Anthropic, AWS Bedrock, and OpenAI, remove the init-time arg entirely since it was never shipped.
Still need to handle realtime services (OpenAI Realtime, Grok Realtime, Gemini Live).
