feat: enhance OaiResponsesStreamHandler to handle output text and improve response streaming

dto/openai_response.go

@@ -237,8 +237,19 @@ type ResponsesOutputContent struct {
 	Annotations []interface{} `json:"annotations"`
 }
 
+const (
+	BuildInTools_WebSearch  = "web_search_preview"
+	BuildInTools_FileSearch = "file_search"
+)
+
+const (
+	ResponsesOutputTypeItemAdded = "response.output_item.added"
+	ResponsesOutputTypeItemDone  = "response.output_item.done"
+)
+
 // ResponsesStreamResponse 用于处理 /v1/responses 流式响应
 type ResponsesStreamResponse struct {
 	Type     string                   `json:"type"`
 	Response *OpenAIResponsesResponse `json:"response"`
+	Delta    string                   `json:"delta,omitempty"`
 }