chore(ai-gateway): map all OpenRouter -latest aliases to Vercel

[kilo-code-bot]

Summary

• Add Vercel mappings for the two remaining OpenRouter ~*-latest aliases: ~google/gemini-flash-latest → google/gemini-3-flash and ~openai/gpt-mini-latest → openai/gpt-5.4-mini.
• Introduce GEMINI_FLASH_CURRENT_* and GPT_MINI_CURRENT_* constants alongside the existing pro/gpt constants so the targets can be bumped in one place.
• Remove the arcee-ai/trinity-large-preview:free mapping since that :free variant no longer exists on OpenRouter (the forbidden-free-models entry already covers stale clients).

Verification

• Diffed the -latest set on https://openrouter.ai/api/v1/models against the existing map and against https://ai-gateway.vercel.sh/v1/models to confirm every right-hand-side id still exists on the Vercel gateway.
• Updated mapModelIdToVercel.test.ts accordingly; test DB wasn't available locally to run the Jest suite, but pnpm --filter web typecheck passes.

Visual Changes

N/A

Reviewer Notes

• GEMINI_FLASH_CURRENT_VERCEL_MODEL_ID is set to google/gemini-3-flash. If you'd prefer google/gemini-3.1-flash-lite-preview or similar, it's a one-line swap.
• Full pnpm typecheck across the monorepo was skipped in favor of the targeted pnpm --filter web typecheck for turnaround time.

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (4 files)

• apps/web/src/lib/ai-gateway/providers/google.ts
• apps/web/src/lib/ai-gateway/providers/openai.ts
• apps/web/src/lib/ai-gateway/providers/vercel/mapModelIdToVercel.ts
• apps/web/src/lib/ai-gateway/providers/vercel/mapModelIdToVercel.test.ts

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_{Reviewed by gpt-5.5-2026-04-23 · 135,810 tokens}