feat(ai-gateway): allow Responses API for OpenCode Go

[chrarnoldus]

Summary\n- allow the Responses API for the OpenCode Go direct BYOK provider\n- add a regression test for the provider capability\n\n## Verification\n- pnpm --filter web test -- src/lib/ai-gateway/providers/direct-byok/opencode-go.test.ts --runInBand\n- pnpm --filter web typecheck\n- pnpm exec oxlint --config .oxlintrc.json apps/web/src/lib/ai-gateway/providers/direct-byok/opencode-go.ts apps/web/src/lib/ai-gateway/providers/direct-byok/opencode-go.test.ts

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Executive Summary

Adds 'responses' to the OpenCode Go direct-BYOK provider's supported_chat_apis with a regression test; the change matches the established pattern used by other providers (martian, orcarouter), auth for the Responses path is covered by the standard Authorization: Bearer header set in upstreamRequest, and the Anthropic-only x-api-key transform correctly remains scoped to messages requests.

Files Reviewed (2 files)

• apps/web/src/lib/ai-gateway/providers/direct-byok/opencode-go.ts
• apps/web/src/lib/ai-gateway/providers/direct-byok/opencode-go.test.ts

---

_{Reviewed by kimi-k3 · Input: 54.7K · Output: 5.8K · Cached: 532.5K}

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