fix(ui): port retail window control feedback

Map synthetic move and resize affordances to the exact DAT cursors, make chat top chrome movable, and replace stale primary-panel height caps with a dynamic screen-edge constraint. This keeps the retained wrapper adaptation aligned with retail Dragbar/Resizebar behavior.

src/AcDream.App/UI/UiElement.cs

@@ -188,6 +188,13 @@ public abstract class UiElement
     /// <c>gmRadarUI::MoveTo</c> enables this; most windows retain the toolkit default.</summary>
     public bool ConstrainDragToParent { get; set; }
 
+    /// <summary>
+    /// Clamp resize growth to the current parent extent. This is distinct from
+    /// <see cref="ConstrainDragToParent"/>: retail's shared main-panel host may be
+    /// moved freely, but its bottom resizebar grows only to the desktop edge.
+    /// </summary>
+    public bool ConstrainResizeToParent { 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; }