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

docs/api/threading/task-system-config/worker-thread-count.md

@@ -0,0 +1,25 @@
+# TaskSystemConfig::workerThreadCount
+
+```cpp
+uint32_t workerThreadCount = 0
+```
+
+工作线程数量。当值为 0 时，任务系统自动检测 `std::thread::hardware_concurrency()` 并使用该值。
+
+**类型：** `uint32_t`
+
+**默认值：** `0`（自动检测）
+
+**示例：**
+
+```cpp
+TaskSystemConfig config;
+config.workerThreadCount = 4; // 使用 4 个工作线程
+
+TaskSystemConfig autoConfig;
+autoConfig.workerThreadCount = 0; // 自动检测（推荐）
+```
+
+## 相关文档
+
+- [TaskSystemConfig 总览](tasksystemconfig.md) - 返回类总览