[TheGreatAxios]

Closes CL-12065

A refusal block in history no longer throws in buildRequest.

• Typed shape, assistant turn: { type: "refusal", refusal: reason }.
• Flat shape or non-assistant turn: reason as a text part.

Wire shape: openai-node responses.ts (master) lists ResponseOutputMessage in ResponseInputItem, with content: Array<ResponseOutputText | ResponseOutputRefusal> and ResponseOutputRefusal = { type: 'refusal'; refusal: string }. The SDK type also requires id and status; we omit them, as the existing output_text replay already does.

Live API check: pending, not run (no key). If the API rejects the refusal part, the fallback is to replay the reason as { type: "output_text", text: reason } on typed assistant turns, so every shape sends text.

[linear-code]

CL-12065

[TheGreatAxios]

Live check, gpt-5-mini on api.openai.com, all open PRs merged locally: a history with an assistant refusal part followed by a new user turn returns 200, and the model replies normally. The fallback isn't needed.