Implement MiniMax chat completions adapter

[Photon101]

Summary

• replace the MiniMax stub with a real OpenAI-compatible chat completions adapter
• use the documented MiniMax OpenAI-compatible base URL and current M2 model IDs
• support dry-run behavior, standard generation options, opts.extra passthrough for MiniMax options such as reasoning_split, token usage mapping, and concise HTTP error excerpts
• add focused tests for dry-run behavior, request payload/auth, token usage mapping, and error handling

References

• https://platform.minimax.io/docs/api-reference/text-openai-api
• https://platform.minimax.io/docs/api-reference/api-overview

Validation

• corepack pnpm exec vitest run packages/ai/minimax/src/index.test.ts
• corepack pnpm exec tsc -p packages/ai/minimax/tsconfig.json --noEmit
• git diff --check

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[github-actions]

🤖 Auto-rebase: The branch was rebased successfully locally but could not be pushed to the fork. Please enable 'Allow edits from maintainers' in the PR settings, or rebase manually: git fetch upstream master && git rebase upstream/master.

[github-actions]

🤖 Auto-rebase: The branch was rebased successfully locally but could not be pushed to the fork. Please enable 'Allow edits from maintainers' in the PR settings, or rebase manually: git fetch upstream master && git rebase upstream/master.

[github-actions]

🤖 Auto-rebase: The branch was rebased successfully locally but could not be pushed to the fork. Please enable 'Allow edits from maintainers' in the PR settings, or rebase manually: git fetch upstream master && git rebase upstream/master.