fix: improve tab safety and app feedback

src/index.html

@@ -1275,6 +1275,8 @@
                         </div>
                     </div>
 
+                    <div id="pdf-status-message" class="info-message hidden" aria-live="polite"></div>
+
                     <!-- Progress indicator -->
                     <div id="pdf-progress" class="batch-progress hidden">
                         <div class="progress-bar">
@@ -1605,4 +1607,4 @@
     <script src="utils/ModalManager.js"></script>
     <script src="renderer.js"></script>
 </body>
-</html>
+</html>