phsl / new-api

The Instructions field in OpenAIResponsesResponse was defined as string,
but upstream providers may return null or non-string JSON values for this
field. This causes json.Unmarshal to fail, resulting in HTTP 500 on
/v1/responses endpoint.

Other fields in the same struct (Status, ToolChoice, Truncation, etc.)
already use json.RawMessage. The request-side DTO (openai_request.go)
also defines Instructions as json.RawMessage. This fix aligns the
response-side with both patterns.

Co-authored-by: 40005415C\Administrator <linbin@envicool.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>