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/ActivationHandler.cs

@@ -1,3 +1,4 @@
+using Ghost.Editor.Core.Contracts;
 using Ghost.Editor.Core.Utilities;
 using Ghost.Editor.Models;
 using Ghost.Engine;
@@ -64,8 +65,14 @@ internal static class ActivationHandler
         };
 
         AllocationManager.Initialize(opts);
-        
-        App.GetService<EngineCore>();
+
+        var assetRegistry = App.GetService<IAssetRegistry>();
+        var engineCore = App.GetService<EngineCore>();
+
+        assetRegistry.OnAssetImported += (sender, e) =>
+        {
+            engineCore.AssetManager.ReimportAsset(e);
+        };
 
         return ValueTask.CompletedTask;
     }