Realtime: connect()/update_session() can't set turn_detection, language, context_bias; turn.* events parsed as UnknownRealtimeEvent #648

In mistralai 3.5.0 (and main @ 89da0f8), the generated models support turn detection (TurnDetectionStartEvent, TurnDetectionEndEvent, RealtimeTranscriptionSessionUpdatePayload.turn_detection), but the hand-written realtime layer in src/mistralai/extra/realtime/ doesn't expose them:

1. RealtimeTranscription.connect() and RealtimeConnection.update_session() only accept audio_format and target_streaming_delay_ms. There's no way to set turn_detection, language or context_bias, which the realtime docs list as session fields (https://docs.mistral.ai/studio/audio/speech-to-text/transcribe-in-realtime).
2. _MESSAGE_MODELS in extra/realtime/connection.py has no entries for turn.start, turn.eager_end, turn.resume, turn.end, so they're returned as UnknownRealtimeEvent.

Expected: session fields from the docs can be passed through the SDK, and turn events are parsed into their models.

Workaround: a raw WebSocket as in the docs examples, or reading UnknownRealtimeEvent.content.