feat(dock): add core data models for docking system

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

@@ -0,0 +1,27 @@
+using System.Collections.ObjectModel;
+using CommunityToolkit.Mvvm.ComponentModel;
+using Microsoft.UI.Xaml.Controls;
+
+namespace Ghost.Editor.Core.Controls.Internal.Docking;
+
+public partial class DockGroupNode : DockNode
+{
+    [ObservableProperty]
+    private Orientation _orientation = Orientation.Horizontal;
+
+    public ObservableCollection<DockNode> Children { get; } = new();
+
+    public void AddChild(DockNode node)
+    {
+        node.Parent = this;
+        Children.Add(node);
+    }
+
+    public void RemoveChild(DockNode node)
+    {
+        if (Children.Remove(node))
+        {
+            node.Parent = null;
+        }
+    }
+}

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

@@ -0,0 +1,9 @@
+using CommunityToolkit.Mvvm.ComponentModel;
+
+namespace Ghost.Editor.Core.Controls.Internal.Docking;
+
+public abstract partial class DockNode : ObservableObject
+{
+    [ObservableProperty]
+    private DockGroupNode? _parent;
+}

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

@@ -0,0 +1,15 @@
+using System.Collections.ObjectModel;
+using CommunityToolkit.Mvvm.ComponentModel;
+
+namespace Ghost.Editor.Core.Controls.Internal.Docking;
+
+public partial class DockPanelNode : DockNode
+{
+    public ObservableCollection<object> Items { get; } = new();
+
+    [ObservableProperty]
+    private int _selectedIndex = -1;
+
+    [ObservableProperty]
+    private object? _selectedItem;
+}