New `XAISTTService` wraps xAI's real-time speech-to-text WebSocket
(`wss://api.x.ai/v1/stt`). It extends `WebsocketSTTService`, authenticates
with the `XAI_API_KEY` as a Bearer token on the WS handshake, and streams
raw audio (PCM/mu-law/A-law) with configurable interim results, endpointing,
language, multichannel, and diarization settings.
- `src/pipecat/services/xai/stt.py`: new service, settings dataclass, and
`language_to_xai_stt_language` helper.
- `src/pipecat/services/stt_latency.py`: `XAI_TTFS_P99` default.
- `pyproject.toml` / `uv.lock`: `xai` extra now pulls in `websockets-base`.
- `README.md`: link to xAI STT in the services table.
- `examples/voice/voice-xai.py`: swap DeepgramSTTService for XAISTTService so
the xAI voice example is fully xAI.
- `examples/transcription/transcription-xai.py`: new transcription-only
example using the new service.
Example files like openai.py shadow installed packages when Python adds the
script directory to sys.path. Prepend the parent folder name to each example
file (e.g. openai.py -> function-calling-openai.py). Also split
thinking-and-mcp/ into separate mcp/ and thinking/ directories.
