fix(ui): restore retail vitals and window interactions

src/AcDream.App/UI/UiElement.cs

@@ -121,6 +121,16 @@ public abstract class UiElement
     /// </summary>
     public uint SourceLayoutDid { get; internal set; }
 
+    /// <summary>
+    /// Optional game object represented by this retained widget for retail's
+    /// global found-object cursor. Most widgets leave this unset. The toolbar
+    /// inventory/backpack button supplies the player object: retail treats that
+    /// button as the self/backpack target (the same target used by its click and
+    /// drop paths), so hovering it selects the Found cursor family even though
+    /// the authored element is a Button rather than a UIItem.
+    /// </summary>
+    public Func<uint>? FoundObjectGuidProvider { get; set; }
+
     /// <summary>
     /// #409: mirrors <c>ElementInfo.TooltipTextChildElementId</c> (dat
     /// property <c>0x4A</c>). Meaningful only when read off a tooltip