fix(dock): address reviewer feedback on drag state and boundary tests

src/Editor/Ghost.Editor.Core/Controls/Internal/Docking/DockMath.cs

@@ -3,7 +3,7 @@ namespace Ghost.Editor.Core.Controls.Internal.Docking;
 /// <summary>
 /// Defines the possible dock positions for a drop operation.
 /// </summary>
-public enum DockPosition
+internal enum DockPosition
 {
     Center,
     Top,
@@ -16,7 +16,7 @@ public enum DockPosition
 /// <summary>
 /// Helper class for docking-related calculations.
 /// </summary>
-public static class DockMath
+internal static class DockMath
 {
     /// <summary>
     /// Calculates the dock position based on the relative position within a target element.
@@ -24,6 +24,12 @@ public static class DockMath
     /// </summary>
     public static DockPosition CalculateDockPosition(double width, double height, double x, double y, double threshold)
     {
+        // Guard against invalid inputs
+        if (width <= 0 || height <= 0) return DockPosition.None;
+        
+        // Clamp threshold to valid range [0, 0.5]
+        threshold = Math.Max(0, Math.Min(0.5, threshold));
+
         if (x < width * threshold) return DockPosition.Left;
         if (x > width * (1 - threshold)) return DockPosition.Right;
         if (y < height * threshold) return DockPosition.Top;