fix(confirmation): preserve real latency on grace-pending rows instead of zeroing (#756)

A pending (held) row was written with latency 0, losing the measured latency and
denting the latency chart during every grace window (and discarding a recovering
check's real latency). Keep the observed latency; only drop the error text so a
held row never shows a status-contradicting failure message.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/lib/server/queues/monitorExecuteQueue.ts

@@ -140,7 +140,9 @@ const addWorker = () => {
         });
         realtimeData[ts].status = resolved.status;
         if (resolved.pendingHold) {
-          realtimeData[ts].latency = 0;
+          // Hold the confirmed side for display, but keep the real measured latency — zeroing it
+          // would lose data and dent the latency chart during every grace window. Only the error
+          // text is dropped so a held row never shows a status-contradicting failure message.
           delete realtimeData[ts].error_message;
         }
       }