feat: pause Today during mobile Insights (Closes #1082)

frontend/index.html

@@ -309,6 +309,10 @@
       <div><h2 id="insights-heading">Insights</h2><p class="small muted">Context, activity, live signals, and workspace tools.</p></div>
       <button id="close-insights" type="button">Close</button>
     </div>
+    <aside class="today-detour-interruption" data-today-detour role="status" aria-live="polite" hidden>
+      <strong data-today-detour-label>Today paused</strong>
+      <button data-return-from-detour type="button">Return to Today</button>
+    </aside>
   <aside class="sidebar">
     <details class="panel stack" data-panel-key="context" open>
       <summary><h2>Context &amp; view</h2></summary>