fix: Improve OpenAI stream data parsing

relay/adaptor/openai/main.go

@@ -34,7 +34,7 @@ func StreamHandler(c *gin.Context, resp *http.Response, relayMode int) (*model.E
 
 	doneRendered := false
 	for scanner.Scan() {
-		data := scanner.Text()
+		data := NormalizeDataLine(scanner.Text())
 		if len(data) < dataPrefixLength { // ignore blank line or wrong format
 			continue
 		}

relay/adaptor/openai/util.go

@@ -21,3 +21,11 @@ func ErrorWrapper(err error, code string, statusCode int) *model.ErrorWithStatus
 		StatusCode: statusCode,
 	}
 }
+
+func NormalizeDataLine(data string) string {
+	if strings.HasPrefix(data, "data:") {
+		content := strings.TrimLeft(data[len("data:"):], " ")
+		return "data: " + content
+	}
+	return data
+}