refactor(gateway): centralize free model response rewrites

[kilo-code-bot]

Summary

• Move free and stealth model response rewrite eligibility into rewriteFreeModelResponse so the route only delegates the response handling decision.
• Keep API-specific rewrite behavior centralized while preserving the existing safe response fallback when no rewrite is needed.

Verification

• N/A

Visual Changes

• N/A

Reviewer Notes

• N/A

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Executive Summary

Clean refactor that correctly centralizes the free/stealth model response rewrite eligibility checks into rewriteFreeModelResponse, with exact logic equivalence preserved. The incremental commit contains only a cosmetic formatting change (collapsing a two-line variable declaration onto one line) — no semantic changes.

Files Reviewed (2 files)

• apps/web/src/app/api/openrouter/[...path]/route.ts
• apps/web/src/lib/rewriteModelResponse.ts

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