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/App.xaml

@@ -10,7 +10,6 @@
             <ResourceDictionary.MergedDictionaries>
                 <XamlControlsResources xmlns="using:Microsoft.UI.Xaml.Controls" />
                 <ResourceDictionary Source="/Themes/Generic.xaml" />
-                <!--<ResourceDictionary Source="/Themes/DockingDictionary.xaml" />-->
                 <core:ControlsDictionary />
             </ResourceDictionary.MergedDictionaries>
         </ResourceDictionary>