fix: update token usage calculation

relay/channel/openai/relay_responses.go

@@ -103,12 +103,14 @@ func OaiResponsesStreamHandler(c *gin.Context, info *relaycommon.RelayInfo, resp
 			// 非正常结束，使用输出文本的 token 数量
 			completionTokens := service.CountTextToken(tempStr, info.UpstreamModelName)
 			usage.CompletionTokens = completionTokens
-
-			if usage.PromptTokens == 0 {
-				usage.PromptTokens = info.PromptTokens
-			}
 		}
 	}
 
+	if usage.PromptTokens == 0 && usage.CompletionTokens != 0 {
+		usage.PromptTokens = usage.CompletionTokens
+	} else {
+		usage.TotalTokens = usage.PromptTokens + usage.CompletionTokens
+	}
+
 	return usage, nil
 }