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/read-write-lock/readlock.md

@@ -0,0 +1,41 @@
+# ReadWriteLock::ReadLock
+
+```cpp
+void ReadLock()
+```
+
+获取读锁。如果有写者持有锁或正在等待写锁，当前线程将阻塞，直到所有写者完成。
+
+**参数：** 无
+
+**返回：** 无
+
+**线程安全：** ✅
+
+**复杂度：** 平均 O(1)
+
+**注意：**
+- 多个读者可以同时持有读锁。
+- 写锁具有优先权——正在等待的写者会阻塞新的读者，防止写者饥饿。
+- 读锁不可重入，同一线程不可嵌套持有读锁。
+
+**示例：**
+
+```cpp
+#include "XCEngine/Threading/ReadWriteLock.h"
+
+XCEngine::Threading::ReadWriteLock rwLock;
+int sharedValue = 0;
+
+int ReadValue() {
+    rwLock.ReadLock();
+    int value = sharedValue;
+    rwLock.ReadUnlock();
+    return value;
+}
+```
+
+## 相关文档
+
+- [`ReadWriteLock`](readwritelock.md) - 返回类总览
+- [`ReadUnlock`](readunlock.md) - 释放读锁