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/Windows/EngineEditorWindow.xaml

@@ -66,6 +66,7 @@
                     Text="Edit" />
                 <SelectorBarItem x:Name="AnalysisSelectorItem" Text="Analysis" />
                 <SelectorBarItem x:Name="BuildSelectorItem" Text="Build" />
+                <SelectorBarItem x:Name="SettingsSelectorItem" Text="Settings" />
             </SelectorBar>
         </StackPanel>