feat(kon): add semantic HTML and ARIA labels — main wrapper, live regions, button labels

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

src/lib/pages/TasksPage.svelte

@@ -232,6 +232,7 @@
 
   <!-- Bucket tabs + sort -->
   <div class="flex items-center gap-1 px-7 pb-3">
+    <nav aria-label="Task filters">
     {#each buckets as bucket}
       <button
         class="flex items-center gap-1.5 btn-md rounded-lg transition-colors
@@ -251,6 +252,7 @@
         {/if}
       </button>
     {/each}
+    </nav>
 
     <div class="flex-1"></div>
 
@@ -259,6 +261,7 @@
       <button
         class="flex items-center gap-1 px-2 py-1.5 rounded-lg text-[11px] text-text-tertiary hover:text-text-secondary hover:bg-hover"
         onclick={() => showSortMenu = !showSortMenu}
+        aria-label="Sort tasks"
       >
         <svg class="w-3.5 h-3.5" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
           <path d="M3 6h18M3 12h12M3 18h6" stroke-linecap="round" />
@@ -290,6 +293,7 @@
       <button
         class="flex items-center justify-center h-[32px] text-text-tertiary hover:text-text-secondary border-b border-border-subtle"
         onclick={() => sidebarCollapsed = !sidebarCollapsed}
+        aria-label={sidebarCollapsed ? "Expand list sidebar" : "Collapse list sidebar"}
       >
         <svg class="w-3 h-3 transition-transform {sidebarCollapsed ? 'rotate-180' : ''}" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
           <path d="M15 18l-6-6 6-6" stroke-linecap="round" stroke-linejoin="round" />
@@ -494,6 +498,7 @@
                     {/if}
                   </div>
                   <button
+                    aria-label="Delete completed task"
                     class="mt-0.5 text-text-tertiary hover:text-danger opacity-0 group-hover:opacity-100 transition-opacity"
                     onclick={() => deleteTask(task.id)}
                   >