feat: add MiniMax as a first-class AI provider (M2.7 default)

[octo-patch]

Summary

Add MiniMax as a first-class AI provider via Vercel AI SDK OpenAI-compatible adapter, with M2.7 as default model.

Changes

• Add MiniMax provider to model factory (OpenAI-compatible via @ai-sdk/openai)
• Add MiniMax-M2.7 and MiniMax-M2.7-highspeed to model selection list (default)
• Add MiniMax-M2.5 and MiniMax-M2.5-highspeed as alternative models
• Add MiniMax API key management in config and UI
• API Base URL: https://api.minimax.io/v1

Why

MiniMax-M2.7 is the latest flagship model with enhanced reasoning and coding capabilities.

Testing

• All 766 existing unit tests pass
• Integration tested with MiniMax API

[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!