docs: update memory and threading API docs

docs/api/memory/pool-allocator/get-peak-allocated.md

@@ -0,0 +1,33 @@
+# PoolAllocator::GetPeakAllocated
+
+```cpp
+size_t GetPeakAllocated() const override;
+```
+
+返回峰值分配的内存总量（字节）。由于池在构造时预分配所有块，峰值即为 `m_totalBlocks * m_blockSize`。
+
+**参数：** 无
+
+**返回：** 内存池总容量（字节）
+
+**复杂度：** O(1)
+
+**示例：**
+
+```cpp
+#include <XCEngine/Memory/PoolAllocator.h>
+
+PoolAllocator pool(sizeof(int), 100);
+
+size_t peak = pool.GetPeakAllocated(); // 100 * sizeof(int)
+
+// 即使分配了部分块，峰值仍然是总容量
+void* block1 = pool.Allocate();
+void* block2 = pool.Allocate();
+size_t current = pool.GetTotalAllocated(); // 2 * sizeof(int)
+peak = pool.GetPeakAllocated();            // 100 * sizeof(int)
+```
+
+## 相关文档
+
+- [PoolAllocator 总览](pool-allocator.md) - 返回类总览