fix(opencode): resolve Mistral tool→user message ordering error

[dfischer-mw]

Issue

Fixes #7488

Problem

When using Mistral or Devstral models with tool calls (especially via vLLM or openai-compatible endpoints), requests fail with:

  mistral_common.exceptions.InvalidMessageStructureException:
  Unexpected role 'user' after role 'tool'

I guess this occurs because Mistral enforces strict message ordering: a tool message must be followed by an assistant message before any user message.

I then looked in the code and saw the transform logic to fix message ordering already existed in transform.ts, but it never ran because the middleware in llm.ts line 187 was transforming the wrong parameter (args.params.prompt instead of args.params.messages) (im TS noob so please help me out here if wrong).

The changes I did:

1. The middleware stuff in src/session/llm.ts: Changed transform to target args.params.messages instead of prompt
2. Then included more model name variants (src/provider/transform.ts): Now detects Mistral variants including:
   • Devstral models
   • Models served via openai-compatible providers
   • Checks both model.id and model.api.id
3. Up tests(test/provider/transform.test.ts): 6 new

The flow should now be from user → assistant (tool_calls) → tool → user to user → assistant (tool_calls) → tool → assistant ("Done.") → user
I hope this meets your standards. :)

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

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