Refactored Vertex to use float3 position/normal, float2 uv, float4 tangent, and Color128 color, updating all mesh generation and HLSL code accordingly. Added MeshUtility for loading .obj/.fbx meshes with deduplication and normal/tangent computation. Updated GraphicsTestWindow to use the new loader and improved resource management. Fixed D3D12ResourceAllocator resource creation logic, improved camera projection math, and simplified RenderingLayerMask. Updated package references and app display name.
BREAKING CHANGE: Vertex struct layout changed; all mesh code and shaders must use the new format.
