refactor: improve test infrastructure and fix OpenGL GLAD initialization

- Rename D3D12Enum.h to D3D12Enums.h for naming consistency
- Fix OpenGL unit test GLAD initialization by using gladLoadGL()
  instead of gladLoadGLLoader(wglGetProcAddress) for fallback support
- Migrate remaining tests to use gtest_discover_tests for granular
  test discovery (math, core, containers, memory, threading, debug,
  components, scene, resources, input, opengl)
- Remove obsolete TEST_RESOURCES_DIR and copy_directory commands
  from OpenGL unit test CMakeLists (minimal/Res doesn't exist)
- Update TEST_SPEC.md with performance metrics and per-module
  build/test commands for faster development workflow
- Update CMake path references to use lowercase paths

engine/include/XCEngine/RHI/D3D12/D3D12Buffer.h

@@ -5,7 +5,7 @@
 #include <string>
 
 #include "../RHIBuffer.h"
-#include "D3D12Enum.h"
+#include "D3D12Enums.h"
 
 using Microsoft::WRL::ComPtr;
 

engine/include/XCEngine/RHI/D3D12/D3D12CommandList.h

@@ -8,7 +8,7 @@
 #include "../RHICommandList.h"
 #include "../RHIEnums.h"
 #include "../RHITypes.h"
-#include "D3D12Enum.h"
+#include "D3D12Enums.h"
 
 using Microsoft::WRL::ComPtr;
 

engine/include/XCEngine/RHI/D3D12/D3D12CommandQueue.h

@@ -5,7 +5,7 @@
 
 #include "../RHICommandQueue.h"
 #include "../RHIEnums.h"
-#include "D3D12Enum.h"
+#include "D3D12Enums.h"
 
 using Microsoft::WRL::ComPtr;
 

engine/include/XCEngine/RHI/D3D12/D3D12DepthStencilView.h

@@ -4,7 +4,7 @@
 #include <wrl/client.h>
 
 #include "../RHIEnums.h"
-#include "D3D12Enum.h"
+#include "D3D12Enums.h"
 
 using Microsoft::WRL::ComPtr;
 

engine/include/XCEngine/RHI/D3D12/D3D12DescriptorHeap.h

@@ -6,7 +6,7 @@
 #include "../RHIEnums.h"
 #include "../RHITypes.h"
 #include "../RHIDescriptorPool.h"
-#include "D3D12Enum.h"
+#include "D3D12Enums.h"
 
 using Microsoft::WRL::ComPtr;
 

engine/include/XCEngine/RHI/D3D12/D3D12Device.h

@@ -9,7 +9,7 @@
 #include "../RHIDevice.h"
 #include "../RHIEnums.h"
 #include "../RHITypes.h"
-#include "D3D12Enum.h"
+#include "D3D12Enums.h"
 
 using Microsoft::WRL::ComPtr;
 

engine/include/XCEngine/RHI/D3D12/D3D12Enums.h

@@ -293,4 +293,4 @@ inline D3D12_COMMAND_LIST_TYPE ToD3D12(CommandQueueType type) {
 }
 
 } // namespace RHI
-} // namespace XCEngine
+} // namespace XCEngine

engine/include/XCEngine/RHI/D3D12/D3D12PipelineState.h

@@ -6,7 +6,7 @@
 
 #include "../RHIPipelineState.h"
 #include "../RHIEnums.h"
-#include "D3D12Enum.h"
+#include "D3D12Enums.h"
 
 using Microsoft::WRL::ComPtr;
 

engine/include/XCEngine/RHI/D3D12/D3D12QueryHeap.h

@@ -4,7 +4,7 @@
 #include <wrl/client.h>
 #include <cstdint>
 
-#include "D3D12Enum.h"
+#include "D3D12Enums.h"
 
 using Microsoft::WRL::ComPtr;
 

engine/include/XCEngine/RHI/D3D12/D3D12RenderTargetView.h

@@ -4,7 +4,7 @@
 #include <wrl/client.h>
 
 #include "../RHIEnums.h"
-#include "D3D12Enum.h"
+#include "D3D12Enums.h"
 
 using Microsoft::WRL::ComPtr;
 

engine/include/XCEngine/RHI/D3D12/D3D12RootSignature.h

@@ -5,7 +5,7 @@
 #include <vector>
 
 #include "../RHIEnums.h"
-#include "D3D12Enum.h"
+#include "D3D12Enums.h"
 
 using Microsoft::WRL::ComPtr;
 

engine/include/XCEngine/RHI/D3D12/D3D12Sampler.h

@@ -4,7 +4,7 @@
 #include <wrl/client.h>
 
 #include "../RHISampler.h"
-#include "D3D12Enum.h"
+#include "D3D12Enums.h"
 
 using Microsoft::WRL::ComPtr;
 

engine/include/XCEngine/RHI/D3D12/D3D12Shader.h

@@ -6,7 +6,7 @@
 #include <string>
 
 #include "../RHIShader.h"
-#include "D3D12Enum.h"
+#include "D3D12Enums.h"
 #include "../RHITypes.h"
 
 using Microsoft::WRL::ComPtr;

engine/include/XCEngine/RHI/D3D12/D3D12ShaderResourceView.h

@@ -4,7 +4,7 @@
 #include <wrl/client.h>
 
 #include "../RHIEnums.h"
-#include "D3D12Enum.h"
+#include "D3D12Enums.h"
 
 using Microsoft::WRL::ComPtr;
 

engine/include/XCEngine/RHI/D3D12/D3D12SwapChain.h

@@ -6,7 +6,7 @@
 #include <vector>
 
 #include "../RHISwapChain.h"
-#include "D3D12Enum.h"
+#include "D3D12Enums.h"
 #include "D3D12Texture.h"
 
 using Microsoft::WRL::ComPtr;

engine/include/XCEngine/RHI/D3D12/D3D12Texture.h

@@ -5,7 +5,7 @@
 #include <string>
 
 #include "../RHITexture.h"
-#include "D3D12Enum.h"
+#include "D3D12Enums.h"
 
 using Microsoft::WRL::ComPtr;