Fixes Window being too wide/tall when added

Fixes Window being core 'moveable'

This goes considerable way to fixing:
gui-cs/Terminal.Gui#3650

But can consider making the Arrangement property user configureable in the same way that we do with Visible (see TestSettingVisible_False) where user can change the value but it does not manifest in the behavior of the view (only for code gen).

src/Design.cs

@@ -229,6 +229,12 @@ public Design CreateSubControlDesign(string name, View subView)
             tf.KeyDown += (s, e) => e.Handled = true;
         }
 
+        if (subView is Window w)
+        {
+            // prevent control from responding to events
+            w.Arrangement = ViewArrangement.Fixed;
+        }
+
         if (subView is TreeView tree)
         {
             tree.AddObject(new TreeNode("Example Branch 1")

src/ViewFactory.cs

@@ -257,8 +257,9 @@ public static T Create<T>(int? width = null, int? height = null, string? text =
 
         static void SetDefaultDimensions( T v, int width = 5, int height = 1 )
         {
-            v.Width = Math.Max( v.GetContentSize().Width, width );
-            v.Height = Math.Max( v.GetContentSize().Height, height );
+            v.Width = v.Width is DimFill ? width : Math.Max(v.GetContentSize().Width, width);
+
+            v.Height = v.Height is DimFill ? height : Math.Max( v.GetContentSize().Height, height );
         }
     }
 

tests/WindowTests.cs

@@ -0,0 +1,31 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace UnitTests
+{
+    internal class WindowTests : Tests
+    {
+        [Test]
+        public void TestViewFactory_HasSensibleDimensions()
+        {
+            var w = ViewFactory.Create<Window>();
+            Assert.That(w.Width,Is.EqualTo((DimAbsolute)10));
+            Assert.That(w.Height, Is.EqualTo((DimAbsolute)5));
+        }
+
+        [Test]
+        public void TestViewFactory_IsNotVanillaDraggable()
+        {
+            RoundTrip<View, Window>(static (_, w) =>
+            {
+                // When adding a Window to the editor it should not be 'moveable'
+                // This is because the core Terminal.Gui drag will conflict with the TGD dragging.
+                Assert.That(w.Arrangement, Is.EqualTo(ViewArrangement.Fixed));
+
+            }, out _);
+        }
+    }
+}