fix(core): restore tencent hy3 reasoning selection

[jibin7jose]

Issue for this PR

Closes #36812

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

This PR restores the reasoning effort selection (Low, Medium, High) for the Tencent Hy3 (Free) models in the OpenCode app.

The issue occurred because dynamic variant generation in packages/core/src/plugin/variant.ts previously lacked logic to detect and handle the hy3 models. I have updated the generate function to identify hy3 models and provide the low, medium, and high variants, fixing the regression.

How did you verify your code works?

• Verified the logic handles the hy3 model checks in variant.ts.
• Added a new unit test in packages/core/test/plugin/variant.test.ts to ensure hy3 models correctly return the low, medium, and high reasoning effort variants.
• Ran the unit tests locally to confirm they pass successfully.

Screenshots / recordings

N/A

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

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Please:

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2. Add Fixes #<number> or Closes #<number> to this PR description

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[github-actions]

Thanks for updating your PR! It now meets our contributing guidelines. 👍