refactor(core): asset pipeline overhaul & dock removal

- Introduced IAsset interface and refactored asset loading/saving.
- Migrated TextureContentHeader to Ghost.Engine; updated usage.
- Rewrote AssetRegistry, AssetCatalog, ImportCoordinator for new asset flow.
- Added thread-safe ConcurrentHashSet utility.
- Improved EditorApplication folder management/init.
- Updated TextureAssetHandler/TextureProcessor for new import/export.
- Added EditorContentProvider for asset access.
- Updated AssetManager to use new AssetType enum; removed GCHandle.
- Removed all custom docking controls and templates.
- Deleted obsolete ViewModels/Pages (Console, Hierarchy, Inspector, Project).
- Renamed ProjectBrowser to ContentBrowser; updated references.
- Updated NuGet packages, Result conversions, and commit instructions.
- General cleanup: namespaces, dead code, structure.

src/Editor/Ghost.Editor/Ghost.Editor.csproj

@@ -198,6 +198,8 @@
   </ItemGroup>
   <ItemGroup>
     <Folder Include="ContextMenu\" />
+    <Folder Include="ViewModels\Pages\" />
+    <Folder Include="Views\Pages\" />
   </ItemGroup>
   <PropertyGroup Label="Globals" />