Add xAI/Grok and Mistral AI support via Vercel AI SDK

[bhouston]

Add xAI/Grok and Mistral AI support via Vercel AI SDK

Description

This PR adds support for two new AI providers:

1. xAI/Grok via the Vercel AI SDK provider (@ai-sdk/xai)
2. Mistral AI via the Vercel AI SDK provider (@ai-sdk/mistral)

Changes

• Added dependencies for xAI and Mistral AI providers
• Updated ModelProvider type to include 'xai' and 'mistral'
• Updated getModel() function to support the new providers
• Added API key checks for xAI and Mistral AI (XAI_API_KEY and MISTRAL_API_KEY)
• Updated CLI options to include the new providers
• Updated README.md with instructions for the new providers
• Added tests for the new providers

Testing

• Added unit tests for the new providers
• Verified all existing tests pass

References

• xAI Provider: https://sdk.vercel.ai/providers/ai-sdk-providers/xai
• Mistral Provider: https://sdk.vercel.ai/providers/ai-sdk-providers/mistral

Closes #89

[sentry-io]

Suspect Issues

This pull request was deployed and Sentry observed the following issues:

• ‼️ Error: Unknown model provider: grok getModel(config.ts) View Issue

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[github-actions]

🎉 This PR is included in version mycoder-agent-v1.0.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀

[github-actions]

🎉 This PR is included in version mycoder-v1.0.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀