feat(ui): port retail radar and compass

src/AcDream.App/UI/UiElement.cs

@@ -156,6 +156,10 @@ public abstract class UiElement
     /// whose Left/Top are screen coordinates (Root sits at the origin).</summary>
     public bool Draggable { get; set; }
 
+    /// <summary>Clamp a dragged top-level window fully inside its parent. Retail
+    /// <c>gmRadarUI::MoveTo</c> enables this; most windows retain the toolkit default.</summary>
+    public bool ConstrainDragToParent { get; set; }
+
     /// <summary>If true, a left-drag starting near this element's edge/corner
     /// resizes it (window resize). Intended for top-level panels.</summary>
     public bool Resizable { get; set; }