- Added `XAITTSService` for streaming text-to-speech using xAI's WebSocket TTS endpoint (`wss://api.x.ai/v1/tts`). Streams `text.delta` chunks up and base64 `audio.delta` chunks down on the same connection so audio begins flowing before the full utterance finishes synthesizing; complements the batch-HTTP `XAIHttpTTSService`. Defaults to raw PCM output so `TTSAudioRawFrame` needs no decoding. The `xai` optional extra now pulls in `pipecat-ai[websockets-base]`.
