- const T* -> T const* in all headers and implementations
- const T& -> T const& for copy constructor/operator= deletes
- update AGENTS.md to document east const convention
- Replace window class with cbt::opengl::context
- Add buffer resource (VBO, EBO, UBO, SSBO) with move semantics
- Add texture resource with format/type enums and filtering
- Add descriptor_set for Vulkan-style resource binding
- All resources use RAII with proper cleanup
portersky