fix(ai-gateway): maximize Auto Free reasoning

[chrarnoldus]

Summary

• hardcode the strongest supported reasoning configuration for every Auto Free candidate
• carry candidate reasoning settings through weighted routing so client defaults cannot weaken them
• cover the full candidate map and resolved Auto Free result with unit tests

Verification

• pnpm format
• web TypeScript check (apps/web/node_modules/.bin/tsgo --noEmit -p apps/web/tsconfig.json)
• targeted oxlint on the four changed files
• targeted Jest suites: 58 tests passed

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (4 files)

• apps/web/src/lib/ai-gateway/models.ts
• apps/web/src/lib/ai-gateway/models.test.ts
• apps/web/src/lib/ai-gateway/auto-model/resolution.ts
• apps/web/src/lib/ai-gateway/auto-model/resolution.test.ts

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_{Reviewed by kimi-k3 · Input: 68K · Output: 9.6K · Cached: 696.3K}

_{Review guidance: REVIEW.md from base branch main}