feat: add MiniMax as a first-class AI provider

[octo-patch]

Summary

Add MiniMax as a first-class AI provider alongside Anthropic, OpenAI, and Google. MiniMax offers an OpenAI-compatible API with 204K context window models at competitive pricing.

What's included

• Backend: New minimax case in model factory using the existing @ai-sdk/openai adapter with https://api.minimax.io/v1 as the default base URL
• Config: minimax added to the apiKeys schema so users can store their API key in ai-provider-manager.json
• Web UI: MiniMax appears in the AI Provider page's provider selector with two model presets (MiniMax-M2.5, MiniMax-M2.5-highspeed), and in the per-channel LLM Provider dropdown
• Tests: Unit tests for MiniMax model creation, custom base URL, and API key resolution
• Docs: README updated to reference MiniMax

Configuration

{
  "backend": "vercel-ai-sdk",
  "provider": "minimax",
  "model": "MiniMax-M2.5",
  "apiKeys": { "minimax": "your-api-key" }
}

Available models

Model	Context	Input	Output
MiniMax-M2.5	204K tokens	$0.3/M	$1.2/M
MiniMax-M2.5-highspeed	204K tokens	$0.6/M	$2.4/M

China mainland users can set baseUrl to https://api.minimaxi.com/v1.

Test plan

• Unit tests pass (pnpm test — 9 new tests, all green)
• Full test suite passes (775/775 tests pass)
• Backend builds cleanly (pnpm build)
• UI builds cleanly with no TypeScript errors
• MiniMax API integration verified (successful chat completion with MiniMax-M2.5)

[luokerenx4]

Hi @octo-patch, thanks for the contribution! We appreciate the effort.

However, due to security considerations, we're unable to directly accept external PRs at this time.

That said, MiniMax support is something we're thinking about. Currently there are two possible approaches we're considering:

1. Configure MiniMax's Claude-compatible endpoint via Anthropic's Claude Agent SDK
2. Configure MiniMax's Claude-compatible endpoint via the Vercel AI SDK's Claude provider

We haven't decided yet how to best surface this in the frontend for quick switching between providers. Once we've figured that out, we'll close this PR and include your name in the commit as the original proposer.

Thanks again for your interest in the project!

[octo-patch]

Thanks for the response, @luokerenx4! Completely understand the security considerations. Great to hear that MiniMax support is on the roadmap — happy to close this PR if you'd prefer to handle it internally. Let me know if there's anything else I can help with!