perf(ui): scope cooldown heartbeat to visible items

src/AcDream.App/UI/Layout/ItemCooldownUiController.cs

@@ -49,14 +49,22 @@ public sealed class ItemCooldownUiController
 
     public void Tick()
     {
-        double now = _currentTime();
         _stepByItemId.Clear();
+        if (!_spellbook.HasCooldownEnchantments)
+            return;
+
+        double now = _currentTime();
 
         // Retail updates cooldown visibility from UIElement_UIItem::DoHeartbeat,
         // not while drawing. Query each represented item once so an expired
-        // registry node can be removed safely before the render walk.
+        // registry node can be removed safely before the render walk. A hidden
+        // retained subtree receives no heartbeat in retail, so only lists whose
+        // complete ancestry is visible participate.
         foreach (UiItemList list in _lists)
         {
+            if (!IsEffectivelyVisible(list))
+                continue;
+
             for (int index = 0; index < list.GetNumUIItems(); index++)
             {
                 UiItemSlot? cell = list.GetItem(index);
@@ -83,6 +91,17 @@ public sealed class ItemCooldownUiController
         }
     }
 
+    internal static bool IsEffectivelyVisible(UiElement element)
+    {
+        ArgumentNullException.ThrowIfNull(element);
+        for (UiElement? current = element; current is not null; current = current.Parent)
+        {
+            if (!current.Visible)
+                return false;
+        }
+        return true;
+    }
+
     internal int GetOverlayStep(uint itemId)
         => _stepByItemId.TryGetValue(itemId, out int step) ? step : 0;
 

src/AcDream.Core/Spells/Spellbook.cs

@@ -156,6 +156,11 @@ public sealed class Spellbook
 
     public int LearnedCount => _learnedSpells.Count;
     public int ActiveCount  => _activeById.Count;
+    public bool HasCooldownEnchantments =>
+        _enchantmentOrderByBucket.TryGetValue(
+            CooldownBucket,
+            out List<uint>? order)
+        && order.Count != 0;
 
     public bool Knows(uint spellId) => _learnedSpells.ContainsKey(spellId);