agent: fix — remove blocking backdrop from task sidebar entirely

The invisible z-40 overlay was still eating pointer events across the
main content. Removed the backdrop — sidebar now floats without blocking
anything. Close with Escape key.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/routes/+layout.svelte

@@ -214,16 +214,8 @@
     </div>
   </div>
 
-  <!-- Task sidebar as overlay — doesn't shrink main content -->
+  <!-- Task sidebar — floats over content, no blocking overlay -->
   {#if page.taskSidebarOpen && page.current !== "first-run" && !isSecondaryWindow}
-    <!-- Backdrop — below titlebar only, closes sidebar on click -->
-    <!-- svelte-ignore a11y_click_events_have_key_events -->
-    <!-- svelte-ignore a11y_no_static_element_interactions -->
-    <div
-      class="fixed top-[36px] left-0 right-[280px] bottom-0 z-40"
-      onclick={() => { page.taskSidebarOpen = false; }}
-    ></div>
-    <!-- Sidebar panel -->
     <div class="fixed top-[36px] right-0 bottom-0 w-[280px] z-50 shadow-xl">
       <TaskSidebar />
     </div>