- Created tests/Core/Asset/ with tests for IResource, ResourceTypes, ResourceHandle, ResourceCache, ResourceDependencyGraph, ResourceGUID
- Created tests/Core/IO/ with tests for IResourceLoader, ResourcePath, ResourceFileSystem, FileArchive, ResourcePackage
- Reorganized tests/Resources/ into subdirectories: Texture/, Mesh/, Material/, Shader/, AudioClip/
- Added CMakeLists.txt for each new test subdirectory
- Fixed Material.h missing ResourceManager.h include (lost during engine refactor)
- tests/Core/CMakeLists.txt updated to include Asset/ and IO/ subdirectories
