Replace Magick.NET with stb_image; refactor asset pipeline

- Switched image loading/saving from Magick.NET to native stb_image (Ghost.StbI), removing Magick.NET dependency.
- Added Ghost.StbI project with native DLL, P/Invoke bindings, and wrapper.
- Refactored TextureAssetHandler and TextureProcessor for stb_image, memory-mapped IO, and HDR/16-bit support.
- Split IAssetHandler into IImportableAssetHandler and IPackableAssetHandler; updated interfaces to use FileStream.
- Added shader and mesh asset handlers (GraphicsShaderAssetHandler, ComputeShaderAssetHandler, FBXAssetHandler).
- Improved asset registry/catalog path handling and naming consistency.
- Updated asset import pipeline to use new interfaces and trigger engine reimport.
- Enhanced UI toolbar button styles and EditPage layout.
- Added StbIBindingTest, DisableRuntimeMarshalling, and native wrapper attributes.
- Updated wrapper generator for regex derivesFrom; added stbi.json config.
- Removed Magick.NET reference; added Ghost.StbI and Ghost.Ufbx references.
- Miscellaneous bugfixes and code cleanup.

src/Editor/Ghost.Editor/Views/Controls/ContentBrowser.xaml.cs

@@ -33,8 +33,6 @@ internal sealed partial class ContentBrowser : UserControl
 
         Loaded += ProjectBrowser_Loaded;
         Unloaded += ProjectBrowser_Unloaded;
-
-        GettingFocus += ProjectBrowser_GettingFocus;
     }
 
     private void ProjectBrowser_GettingFocus(UIElement sender, GettingFocusEventArgs args)
@@ -50,11 +48,13 @@ internal sealed partial class ContentBrowser : UserControl
     private void ProjectBrowser_Loaded(object sender, RoutedEventArgs e)
     {
         _inspectorService.OnSelectionChanged += _inspectorService_OnSelectionChanged;
+        GettingFocus += ProjectBrowser_GettingFocus;
     }
 
     private void ProjectBrowser_Unloaded(object sender, RoutedEventArgs e)
     {
         _inspectorService.OnSelectionChanged -= _inspectorService_OnSelectionChanged;
+        GettingFocus -= ProjectBrowser_GettingFocus;
 
         if (LastFocused == this)
         {