feat(FN-3608): update dashboard chat documentation

Updated the dashboard chat documentation in the user guide with a minor addition.

Fusion-Task-Id: FN-3608

packages/dashboard/app/hooks/useQuickChat.ts

@@ -557,6 +557,7 @@ export function useQuickChat(
 
         pendingMessageRef.current = content;
         setPendingMessage(content);
+        addToast?.("Still waiting for previous response — message queued", "warning");
         return Promise.resolve();
       }