feat: add Mistral AI plugin with LLM support

[kevinkeibel1]

Description

Changes Made

• Implements LLM and LLMStream using the official @mistralai/mistralai SDK
• Supports streaming, tool calling, parallel tool calls, and tool choice
• Handles all ChatContext item types: messages, function calls, outputs
• Includes test suite using shared @livekit/agents-plugins-test helpers
• Adds MistralChatModels type for all supported model identifiers

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.

restaurant_agent.ts and realtime_agent.ts not tested because no changes to the core code were applied.

[changeset-bot]

🦋 Changeset detected

Latest commit: 6609f67

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

This PR includes changesets to release 23 packages

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

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[CLAassistant]

All committers have signed the CLA.