Add real-time updates for meeting alerts across user devices

Introduce real-time event listeners and emitters to synchronize meeting alert status changes, such as "Done" or "Dismissed", across a user's multiple open tabs and devices. This update refactors the `executive-meetings.ts` route to trigger a per-user socket event upon state transitions, which is then handled by `use-notifications-socket.ts` to invalidate the alert state query, ensuring near-instantaneous UI updates. New tests in `executive-meetings-upcoming-alert.spec.mjs` verify the cross-tab synchronization for both "Done" and "Dismiss" actions, confirming that only the acting user's alerts are affected.

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artifacts/tx-os/src/hooks/use-notifications-socket.ts

@@ -92,6 +92,21 @@ export function useNotificationsSocket() {
       });
     });
 
+    // #277: Per-user push for the 5-min upcoming-meeting alert. The server
+    // only emits this to `user:${userId}`, so receiving it means *this*
+    // user (in this or another of their tabs / devices) acknowledged or
+    // dismissed an alert. Invalidate the alert-state query so the open
+    // alert card hides within ~1s instead of waiting on the 30s poll.
+    // Other users do not receive this event, so their alert stays visible.
+    socket.on(
+      "executive_meeting_alert_state_changed",
+      () => {
+        queryClient.invalidateQueries({
+          queryKey: ["/api/executive-meetings/alert-state"],
+        });
+      },
+    );
+
     socket.on(
       "role_permissions_changed",
       (payload?: { roleId?: number }) => {