Add sub-asset import and mesh asset support

- Implement sub-asset import for mesh/model assets with manifest generation and deterministic GUIDs
- Extend AssetCatalog for sub-asset tracking and management
- Update AssetRegistry and ImportCoordinator for sub-asset workflows
- Add mesh asset parsing, GPU upload, and resource management
- Update mesh data structures for meshlet groups/hierarchy and LODs
- Improve tests for sub-asset import and mesh handling
- Enhance mocks for mesh asset testing and resource mapping
- Fix path handling and native DLL loading issues
- Miscellaneous bug fixes and refactoring

src/Test/Ghost.MicroTest/Program.cs

@@ -1,4 +1,4 @@
 using Ghost.MicroTest;
 using Ghost.Test.Core;
 
-TestRunner.Run<NvttBindingTest>();
+TestRunner.Run<UfbxBindingTest>();