Refactor asset import API and mesh streaming pipeline

- Standardize IImportableAssetHandler.ImportAsync to return sub-asset results
- Remove ISubAssetImportableAssetHandler, merge into main interface
- Update FBX/Texture handlers for new import contract
- Add StreamUtility for efficient (async) binary writes
- Refactor meshlet/LOD building to use ref structs and safe memory
- Use new streaming utilities in mesh import/export and tests
- AssetCatalog.Remove now recursively deletes sub-assets
- Improve asset registry file watcher for better change detection
- Log unhandled exceptions in App instead of breaking
- Add interpolated collection support to NativeMemoryManager
- Update project references and fix minor bugs

src/Editor/Ghost.Editor/App.xaml.cs

@@ -153,6 +153,7 @@ public partial class App : Application
         }
         catch (Exception ex)
         {
+            Logger.Error(ex);
             Environment.Exit(ex.HResult);
         }
     }
@@ -169,7 +170,7 @@ public partial class App : Application
         }
         catch (Exception ex)
         {
-            Debugger.BreakForUserUnhandledException(ex);
+            Logger.Error(ex);
         }
         finally
         {