New test files:
- VulkanStructSizeTests.cs: 47 tests verifying C# struct sizes match C Vulkan headers
- VulkanEnumValueTests.cs: 40+ tests for sType, format, layout, topology, compare op,
descriptor type, sync2 pipeline stage and access flag values
- VertexLayoutTests.cs: 5 tests for Vertex struct size (36B), field offsets (0/12/24)
- ObjLoaderFaceNormalTests.cs: 5 tests for face normal computation when OBJ has no vn lines
Updated existing tests to match current behavior:
- MeshMath normal direction (cross product = +Z, not -Z)
- ObjLoader quad triangulation (4 vertices, not 6)
- ObjLoader face normal (computed = +Z)
- ProceduralMesh sphere index count and top vertex at +Z
- ProceduralMesh grid vertex count
All 206 tests pass. Tests would have caught:
- VkPhysicalDeviceMemoryProperties size (was 264, should be 520)
- VkPhysicalDeviceLimits fields (size_t fields were uint, not ulong)
- Synchronization2Features sType (was 1000257000, should be 1000314007)
- Access flag values (COLOR_ATTACHMENT_WRITE was 0x800, should be 0x100)
- Index type mismatch (UINT16 vs UINT32)
