feat: record stream interruption reasons via StreamStatus

- Add StreamStatus type (relay/common) to track stream end reason
  (done/timeout/client_gone/scanner_error/eof/panic/ping_fail) and
  accumulate soft errors during streaming via sync.Once + sync.Mutex.
- Add StreamResult (relay/helper) as the callback interface: adapters
  call sr.Error() for soft errors, sr.Stop() for fatal, sr.Done() for
  normal completion. No early-return problem — multiple errors per chunk
  are naturally supported.
- Refactor StreamScannerHandler callback from func(string) bool to
  func(string, *StreamResult). All 9 channel adapters updated.
- Write stream_status into log other JSON field (admin-only) with
  status ok/error, end_reason, error_count, and error messages.
- Frontend: display stream status in log detail expansion for admins.

relay/channel/xai/text.go

@@ -43,12 +43,12 @@ func xAIStreamHandler(c *gin.Context, info *relaycommon.RelayInfo, resp *http.Re
 
 	helper.SetEventStreamHeaders(c)
 
-	helper.StreamScannerHandler(c, resp, info, func(data string) bool {
+	helper.StreamScannerHandler(c, resp, info, func(data string, sr *helper.StreamResult) {
 		var xAIResp *dto.ChatCompletionsStreamResponse
-		err := common.UnmarshalJsonStr(data, &xAIResp)
-		if err != nil {
+		if err := common.UnmarshalJsonStr(data, &xAIResp); err != nil {
 			common.SysLog("error unmarshalling stream response: " + err.Error())
-			return true
+			sr.Error(err)
+			return
 		}
 
 		// 把 xAI 的usage转换为 OpenAI 的usage
@@ -61,11 +61,10 @@ func xAIStreamHandler(c *gin.Context, info *relaycommon.RelayInfo, resp *http.Re
 
 		openaiResponse := streamResponseXAI2OpenAI(xAIResp, usage)
 		_ = openai.ProcessStreamResponse(*openaiResponse, &responseTextBuilder, &toolCount)
-		err = helper.ObjectData(c, openaiResponse)
-		if err != nil {
+		if err := helper.ObjectData(c, openaiResponse); err != nil {
 			common.SysLog(err.Error())
+			sr.Error(err)
 		}
-		return true
 	})
 
 	if !containStreamUsage {