feat: add grok plugin

[karlsonlee-livekit]

Description

This PR introduces the @livekit/agents-plugin-xai package, enabling support for xAI's Realtime API (Grok) within the agents-js framework. It reuses the OpenAI plugin's infrastructure while handling xAI-specific configurations and protocol nuances.

Changes Made

• Created @livekit/agents-plugin-xai: Initialized plugin with RealtimeModel implementation.
• Configured Defaults: Set xAI base URL, default model (grok-4-1-fast-non-reasoning), and used server_vad for turn detection.
• Improved Compatibility: Updated [@livekit/agents-plugin-openai] to safely handle optional part fields in response.content_part.done events (required for xAI compatibility).
• Added Example: Included a usage example in examples/src/xai-realtime.ts.

Pre-Review Checklist

• Build passes: All builds (lint, typecheck, tests) pass locally
• AI-generated code reviewed: Removed unnecessary comments and ensured code quality
• Changes explained: All changes are properly documented and justified above
• Scope appropriate: All changes relate to the PR title, or explanations provided for why they're included
• Video demo: A small video demo showing changes works as expected and did not break any existing functionality using Agent Playground (if applicable)

Testing

• Automated tests added/updated (if applicable)
• All tests pass
• Make sure both restaurant_agent.ts and realtime_agent.ts work properly (for major changes)

Additional Notes

---

Note to reviewers: Please ensure the pre-review checklist is completed before starting your review.

[changeset-bot]

🦋 Changeset detected

Latest commit: e363f5e

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 17 packages

Name	Type
@livekit/agents-plugin-openai	Major
@livekit/agents-plugin-xai	Major
@livekit/agents-plugin-anam	Major
@livekit/agents-plugin-cartesia	Major
@livekit/agents-plugin-elevenlabs	Major
@livekit/agents-plugin-google	Major
@livekit/agents-plugin-neuphonic	Major
@livekit/agents-plugin-resemble	Major
@livekit/agents-plugin-rime	Major
@livekit/agents	Major
@livekit/agents-plugin-baseten	Major
@livekit/agents-plugin-bey	Major
@livekit/agents-plugin-deepgram	Major
@livekit/agents-plugin-inworld	Major
@livekit/agents-plugin-livekit	Major
@livekit/agents-plugin-silero	Major
@livekit/agents-plugins-test	Major

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[CLAassistant]

All committers have signed the CLA.

[karlsonlee-livekit]

https://www.loom.com/share/6d840265ff7d416f882242823dc679e5