agent: fix — infinite reactivity loop in TaskSidebar froze entire app

prevTaskIds was declared as $state, causing the $effect that writes to
it to re-trigger itself infinitely (effect_update_depth_exceeded). The
variable is just a comparison reference — doesn't need to be reactive.
Changed to a plain let.

Also removed debug event loggers and reverted grain z-index.

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

src/lib/components/TaskSidebar.svelte

@@ -20,7 +20,9 @@
   }
 
   // Track recently added tasks for highlight animation
-  let prevTaskIds = $state(new Set(tasks.map((t) => t.id)));
+  // Use a plain variable (not $state) for previous IDs to avoid
+  // read-write loop inside the $effect.
+  let prevTaskIds = new Set(tasks.map((t) => t.id));
   $effect(() => {
     const currentIds = new Set(tasks.map((t) => t.id));
     for (const id of currentIds) {

src/routes/+layout.svelte

@@ -14,6 +14,7 @@
 
   const prefs = getPreferences();
 
+
   // Detect secondary windows (float, viewer) — they use +layout@.svelte
   // but as a fallback, hide chrome if the URL matches
   let isSecondaryWindow = $derived(
@@ -211,13 +212,11 @@
       <div class="flex-1 overflow-hidden bg-bg">
         {@render children()}
       </div>
+      {#if page.taskSidebarOpen && page.current !== "first-run"}
+        <div class="w-[280px] min-w-[280px] shadow-xl">
+          <TaskSidebar />
+        </div>
+      {/if}
     </div>
   </div>
-
-  <!-- Task sidebar — floats over content, no blocking overlay -->
-  {#if page.taskSidebarOpen && page.current !== "first-run" && !isSecondaryWindow}
-    <div class="fixed top-[36px] right-0 bottom-0 w-[280px] z-50 shadow-xl">
-      <TaskSidebar />
-    </div>
-  {/if}
 {/if}