feat: pause Today while handling Attention (Closes #595)

frontend/index.html

@@ -147,6 +147,10 @@
         </div>
       </details>
     </div>
+    <aside class="attention-interruption" id="attention-interruption" role="status" aria-live="polite" hidden>
+      <span><strong>Today paused</strong> while handling Attention</span>
+      <button id="return-to-today" type="button">Return to Today</button>
+    </aside>
     <section class="device-readiness-card" id="device-readiness-card" aria-labelledby="device-readiness-heading" hidden>
       <div>
         <strong id="device-readiness-heading">Make this phone work-ready</strong>