docs: 重构 API 文档结构并修正源码准确性

- 重组文档目录结构: 每个模块的概述页移动到模块子目录
- 重命名 index.md 为 main.md
- 修正所有模块文档中的错误:
  - math: FromEuler→FromEulerAngles, TransformDirection 包含缩放, Box 是 OBB, Color::ToRGBA 格式
  - containers: 新增 operator==/!= 文档, 补充 std::hash DJB 算法细节
  - core: 修复 types 链接错误
  - debug: LogLevelToString 返回大写, timestamp 是秒, Profiler 空实现标注, Windows API vs ANSI
  - memory: 修复头文件路径, malloc vs operator new, 新增方法文档
  - resources: 修复 Shader/Texture 链接错误
  - threading: TaskSystem::Wait 空实现标注, ReadWriteLock 重入描述, LambdaTask 链接
- 验证: fix_links.py 确认 0 个断裂引用

docs/api/memory/allocator/get-total-allocated.md

@@ -0,0 +1,50 @@
+# IAllocator::GetTotalAllocated
+
+```cpp
+virtual size_t GetTotalAllocated() const = 0;
+```
+
+返回此分配器自创建以来累计分配的字节总数。这是一个只读查询操作，不会修改任何内部状态。
+
+**参数：** 无
+
+**返回：** 累计已分配的字节数
+
+**复杂度：** O(1)
+
+**示例：**
+
+```cpp
+#include <XCEngine/Memory/IAllocator.h>
+
+class MyAllocator : public IAllocator {
+    size_t m_allocated = 0;
+public:
+    void* Allocate(size_t size, size_t alignment = 0) override {
+        void* ptr = ::operator new(size);
+        m_allocated += size;
+        return ptr;
+    }
+    
+    void Free(void* ptr) override {
+        if (ptr) ::operator delete(ptr);
+    }
+    
+    void* Reallocate(void* ptr, size_t newSize) override { /* ... */ }
+    
+    size_t GetTotalAllocated() const override { return m_allocated; }
+    size_t GetTotalFreed() const override { return 0; }
+    size_t GetPeakAllocated() const override { return m_allocated; }
+    size_t GetAllocationCount() const override { return 0; }
+    const char* GetName() const override { return "MyAllocator"; }
+};
+
+MyAllocator alloc;
+alloc.Allocate(100);
+alloc.Allocate(200);
+size_t total = alloc.GetTotalAllocated(); // 返回 300
+```
+
+## 相关文档
+
+- [IAllocator 总览](allocator.md) - 返回类总览