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

tests/RHI/D3D12/unit/test_command_queue.cpp

@@ -1,23 +1,18 @@
 #include "fixtures/D3D12TestFixture.h"
+#include "XCEngine/RHI/D3D12/D3D12CommandQueue.h"
+
+using namespace XCEngine::RHI;
 
 TEST_F(D3D12TestFixture, CommandQueue_Get_TimestampFrequency) {
-    D3D12_COMMAND_QUEUE_DESC desc = {};
-    desc.Type = D3D12_COMMAND_LIST_TYPE_DIRECT;
-    
-    ComPtr<ID3D12CommandQueue> queue;
-    HRESULT hr = GetDevice()->CreateCommandQueue(&desc, IID_PPV_ARGS(&queue));
-    ASSERT_HRESULT_SUCCEEDED(hr);
-    
-    UINT64 frequency;
-    hr = queue->GetTimestampFrequency(&frequency);
-    ASSERT_HRESULT_SUCCEEDED(hr);
+    ASSERT_NE(GetCommandQueue(), nullptr);
+    UINT64 frequency = GetCommandQueue()->GetTimestampFrequency();
     EXPECT_GT(frequency, 0);
 }
 
 TEST_F(D3D12TestFixture, CommandQueue_Execute_EmptyCommandLists) {
-    GetCommandList()->Reset(GetCommandAllocator(), nullptr);
-    ID3D12CommandList* commandLists[] = { GetCommandList() };
+    GetCommandList()->Reset();
+    void* commandLists[] = { GetCommandList()->GetCommandList() };
     GetCommandQueue()->ExecuteCommandLists(1, commandLists);
     GetCommandList()->Close();
     WaitForGPU();
-}
+}