Refactor project from Ghost.App to Ghost.Editor

Changed the project structure to reflect a shift from `Ghost.App` to `Ghost.Editor`, updating namespaces and class names throughout.

Changed the application class in `App.xaml` and `App.xaml.cs` from `GhostApplication` to `EditorApplication`.

Changed several service interfaces to reside under `Ghost.Editor.Services.Contracts`, including `IInspectorService`, `INotificationService`, and `IProgressService`.

Added `InspectorView` and `InspectorViewModel` classes to manage inspector functionality.

Added `NavigationTabView` and `NavigationTabPage` classes to facilitate navigation within the editor.

Enhanced `WorldNode` and `EntityNode` classes to support scene graph functionality, including serialization and entity management.

Updated the project file `Ghost.Editor.csproj` to reflect the new structure and removed old references.

Modified the solution file `GhostEngine.sln` to remove references to `Ghost.App` and include `Ghost.Editor`.

Updated unit tests to align with the new namespaces and project structure.

Ghost.App/Core/AssetHandle/Asset.cs

@@ -0,0 +1,24 @@
+namespace Ghost.Editor.Core.AssetHandle;
+
+public abstract class Asset
+{
+    /// <summary>
+    /// Get the Guid of the asset.
+    /// </summary>
+    public Guid GUID
+    {
+        get;
+    } = Guid.NewGuid();
+
+    /// <summary>
+    /// True if the asset is a folder, false if it is a file.
+    /// </summary>
+    public bool IsFolder
+    {
+        get;
+    }
+
+    internal void GenerateMetadata()
+    {
+    }
+}

Ghost.App/Core/AssetHandle/AssetDatabase.cs

@@ -0,0 +1,60 @@
+using System.Diagnostics;
+using System.Reflection;
+
+namespace Ghost.Editor.Core.AssetHandle;
+
+public static class AssetDatabase
+{
+    private static readonly Dictionary<string, Action<string>> _assetOpenHandlers = new(StringComparer.OrdinalIgnoreCase);
+
+    static AssetDatabase()
+    {
+        Initialize();
+    }
+
+    internal static void Initialize()
+    {
+        RegisterAssetHandles();
+    }
+
+    private static void RegisterAssetHandles()
+    {
+        var methods = AppDomain.CurrentDomain.GetAssemblies()
+            .SelectMany(a => a.GetTypes())
+            .SelectMany(t => t.GetMethods(BindingFlags.Static | BindingFlags.Public | BindingFlags.NonPublic))
+            .Where(m => m.GetCustomAttribute<AssetOpenHandlerAttribute>() != null &&
+                m.GetParameters().Length == 1 &&
+                m.GetParameters()[0].ParameterType == typeof(string));
+
+        foreach (var method in methods)
+        {
+            var attr = method.GetCustomAttribute<AssetOpenHandlerAttribute>()!;
+            var del = (Action<string>)Delegate.CreateDelegate(typeof(Action<string>), method);
+            foreach (var ext in attr.Extensions)
+            {
+                if (_assetOpenHandlers.ContainsKey(ext))
+                {
+                    throw new InvalidOperationException($"Duplicate handler for extension '{ext}'");
+                }
+
+                _assetOpenHandlers[ext] = del;
+            }
+        }
+    }
+
+    public static void OpenAsset(string path)
+    {
+        var extension = Path.GetExtension(path);
+        if (_assetOpenHandlers.TryGetValue(extension, out var handler))
+        {
+            handler(path);
+        }
+        else
+        {
+            Process.Start(new ProcessStartInfo(path)
+            {
+                UseShellExecute = true
+            });
+        }
+    }
+}

Ghost.App/Core/AssetHandle/AssetOpenHandlerAttribute .cs

@@ -0,0 +1,15 @@
+namespace Ghost.Editor.Core.AssetHandle;
+
+[AttributeUsage(AttributeTargets.Method)]
+public class AssetOpenHandlerAttribute : Attribute
+{
+    public string[] Extensions
+    {
+        get;
+    }
+
+    public AssetOpenHandlerAttribute(params string[] extensions)
+    {
+        Extensions = extensions.Select(e => e.StartsWith('.') ? e.ToLowerInvariant() : '.' + e.ToLowerInvariant()).ToArray();
+    }
+}