fix(ai-gateway): stop treating OpenRouter alpha/beta as free

[chrarnoldus]

Summary

• OpenRouter models with IDs starting with openrouter/ and ending in -alpha or -beta are no longer treated as free.
• Removes isOpenRouterStealthModel from the free-model check (covers cases like openrouter/auto-beta).
• Updates unit tests to expect these models to be paid.

Test plan

• CI unit tests for isFreeModel / models.test.ts
• Confirm openrouter/auto-beta and other openrouter/*-alpha|*-beta IDs require balance / are not free
• Confirm openrouter/free and *:free models remain free

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Executive Summary

Reviewed the removal of the OpenRouter alpha/beta free-model carve-out; the change and its updated tests are internally consistent and no other references to the removed helper remain.

Files Reviewed (3 files)

• apps/web/src/lib/ai-gateway/is-free-model.ts
• apps/web/src/lib/ai-gateway/models.test.ts
• apps/web/src/lib/ai-gateway/models.ts

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_{Reviewed by claude-sonnet-5 · Input: 18 · Output: 3K · Cached: 324.5K}

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