feat: add Mistral AI Devstral 2 model support

[roomote]

This PR attempts to address Issue #9951. Feedback and guidance are welcome.

Summary

Adds support for the new Mistral AI Devstral 2 models as specified in the issue:

Devstral 2 Models

• devstral-latest
• devstral-medium-latest (updated to 256k context window)
• devstral-2512
• Price: 0.4/M input, 2.0/M output
• Context window: 256k
• Image support: enabled

Devstral Small 2 Models

• devstral-small-latest
• labs-devstral-small-2512
• Price: 0.1/M input, 0.3/M output
• Context window: 256k
• Image support: enabled

Additional Changes

• Updated default temperature from 1 to 0.2 as recommended by Mistral Vibe CLI for optimal performance

Testing

• All type checks pass
• All lint checks pass
• All existing tests pass (139 tests)

Closes #9951

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Important

Add support for Mistral AI Devstral 2 models with updated context windows and default temperature in mistral.ts.

• Models:
  • Add devstral-latest, devstral-medium-latest, devstral-2512 to mistralModels with 256k context window, image support, and specific pricing.
  • Add devstral-small-latest, labs-devstral-small-2512 with 256k context window, image support, and specific pricing.
• Configuration:
  • Update MISTRAL_DEFAULT_TEMPERATURE to 0.2 in mistral.ts for Devstral 2 models.

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[roomote]

Rooviewer   See task on Roo Cloud

Review complete. Found 1 issue to address:

• Global temperature change affects all Mistral models, not just Devstral 2

_{Mention @roomote in a comment to request specific changes to this pull request or fix all unresolved issues.}

[roomote]

Changing MISTRAL_DEFAULT_TEMPERATURE from 1 to 0.2 affects ALL Mistral models, not just the new Devstral 2 models. The fallback temperature in src/api/providers/mistral.ts applies this to every Mistral model when no custom temperature is set. The Vibe CLI recommendation for 0.2 is specific to Devstral 2, but this change will alter behavior for existing users of mistral-large-latest, codestral-latest, mistral-small-latest, etc. Consider using the defaultTemperature field in the model definitions to set model-specific temperatures for the new Devstral 2 models instead of changing the global default.

_{Fix it with Roo Code or mention @roomote and request a fix.}