Support x-api-key credentials for custom LLMs

[chrarnoldus]

Summary

• show API key credential JSON guidance when custom LLM credentials are hidden or empty
• add an x-api-key credential type that sends the key in the x-api-key header instead of bearer authorization
• redact x-api-key values in shared header diagnostics

Testing

• CI only, as requested

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (9 files)

• apps/web/src/app/api/openrouter/[...path]/route.test.ts
• apps/web/src/lib/ai-gateway/experiments/build-direct-provider.test.ts
• apps/web/src/lib/ai-gateway/experiments/build-direct-provider.ts
• apps/web/src/lib/ai-gateway/providers/apply-provider-specific-logic.test.ts
• apps/web/src/lib/ai-gateway/providers/get-provider.ts
• apps/web/src/lib/ai-gateway/providers/partner/providers.ts
• apps/web/src/lib/ai-gateway/providers/provider-definitions.ts
• apps/web/src/lib/ai-gateway/providers/types.ts
• apps/web/src/lib/ai-gateway/providers/upstream-request.generation.test.ts

Previous Review Summary (commit c0b902d)

Current summary above is authoritative. Previous snapshots are kept for context only.

Previous review (commit c0b902d)

Status: No Issues Found | Recommendation: Merge

Files Reviewed (10 files)

• apps/web/src/app/admin/custom-llms/CustomLlmsContent.tsx
• apps/web/src/lib/ai-gateway/custom-llm/google-service-account.test.ts
• apps/web/src/lib/ai-gateway/experiments/build-direct-provider.ts
• apps/web/src/lib/ai-gateway/providers/get-provider.ts
• apps/web/src/lib/ai-gateway/providers/types.ts
• apps/web/src/lib/ai-gateway/providers/upstream-request.ts
• apps/web/src/tests/openrouterApi.timeout.test.ts
• packages/db/src/schema-types.ts
• packages/worker-utils/src/redact-headers.test.ts
• packages/worker-utils/src/redact-headers.ts

---

_{Reviewed by grok-4.6 · Input: 162.8K · Output: 5.5K · Cached: 197.2K}

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