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.

web/src/hooks/usage-logs/useUsageLogsData.jsx

@@ -601,6 +601,32 @@ export const useLogsData = () => {
           value: other.request_path,
         });
       }
+      if (isAdminUser && other?.stream_status) {
+        const ss = other.stream_status;
+        const isOk = ss.status === 'ok';
+        const statusLabel = isOk ? '✓ ' + t('正常') : '✗ ' + t('异常');
+        let streamValue = statusLabel + ' (' + (ss.end_reason || 'unknown') + ')';
+        if (ss.error_count > 0) {
+          streamValue += ` [${t('软错误')}: ${ss.error_count}]`;
+        }
+        if (ss.end_error) {
+          streamValue += ` - ${ss.end_error}`;
+        }
+        expandDataLocal.push({
+          key: t('流状态'),
+          value: streamValue,
+        });
+        if (Array.isArray(ss.errors) && ss.errors.length > 0) {
+          expandDataLocal.push({
+            key: t('流错误详情'),
+            value: (
+              <div style={{ maxWidth: 600, whiteSpace: 'pre-line', wordBreak: 'break-word', lineHeight: 1.6 }}>
+                {ss.errors.join('\n')}
+              </div>
+            ),
+          });
+        }
+      }
       if (Array.isArray(other?.po) && other.po.length > 0) {
         expandDataLocal.push({
           key: t('参数覆盖'),

web/src/i18n/locales/en.json

@@ -2678,6 +2678,11 @@
     "请求结束后多退少补": "Adjust after request completion",
     "请求超时，请刷新页面后重新发起 GitHub 登录": "Request timed out, please refresh and restart GitHub login",
     "请求路径": "Request path",
+    "流状态": "Stream Status",
+    "流错误详情": "Stream Error Details",
+    "软错误": "soft errors",
+    "正常": "Normal",
+    "异常": "Abnormal",
     "请求转换": "Request conversion",
     "请求预扣费额度": "Pre-deduction quota for requests",
     "请点击我": "Please click me",