feat(ui): persist retained window layouts

tests/AcDream.App.Tests/UI/Layout/RetailWindowFrameTests.cs

@@ -106,6 +106,59 @@ public sealed class RetailWindowFrameTests
         Assert.False(content.Resizable);
     }
 
+    [Fact]
+    public void HiddenInventory_RestoredExpandedBeforeFirstDraw_GrowsContentsRows()
+    {
+        ImportedLayout layout = FixtureLoader.LoadInventory();
+        UiItemList grid = Assert.IsType<UiItemList>(
+            layout.FindElement(InventoryController.ContentsGridId));
+        grid.Columns = 6;
+        grid.CellWidth = 32f;
+        grid.CellHeight = 32f;
+        grid.Flush();
+        for (int i = 0; i < 102; i++)
+            grid.AddItem(new UiItemSlot());
+
+        var root = new UiRoot { Width = 1280, Height = 720 };
+        RetailWindowHandle handle = RetailWindowFrame.Mount(
+            root,
+            layout.Root,
+            NoTex,
+            new RetailWindowFrame.Options
+            {
+                WindowName = WindowNames.Inventory,
+                Chrome = RetailWindowChrome.NineSlice,
+                ContentWidth = layout.Root.Width,
+                ContentHeight = layout.Root.Height,
+                Visible = false,
+                ResizeX = false,
+                ResizeY = true,
+                ResizableEdges = ResizeEdges.Bottom,
+                MaxHeight = 560f,
+            });
+
+        // Production installs the controller-owned policies after mounting, while
+        // inventory is still hidden, and captures their design baseline immediately.
+        InventoryController.ConfigureResizeLayout(layout);
+
+        // Persistence restores the hidden window before its first visible draw.
+        handle.ResizeTo(handle.Width, 527f);
+        ApplyAnchors(handle.OuterFrame);
+        grid.LayoutCells();
+
+        Assert.Equal(251f, grid.Height);
+        Assert.Equal(42, grid.Children.Count(child => child.Visible));
+    }
+
+    private static void ApplyAnchors(UiElement parent)
+    {
+        foreach (UiElement child in parent.Children)
+        {
+            child.ApplyAnchor(parent.Width, parent.Height);
+            ApplyAnchors(child);
+        }
+    }
+
     private static ElementInfo Constraints(int minHeight, int maxHeight)
     {
         var info = new ElementInfo();