docs: update memory and threading API docs

docs/api/memory/proxy-allocator/get-allocation-count.md

@@ -0,0 +1,37 @@
+# ProxyAllocator::GetAllocationCount
+
+```cpp
+size_t GetAllocationCount() const override;
+```
+
+获取当前未释放的分配次数。
+
+**参数：** 无
+
+**返回：** 当前未释放的分配次数
+
+**线程安全：** ✅
+
+**复杂度：** O(1)
+
+**示例：**
+
+```cpp
+#include <XCEngine/Memory/MemoryManager.h>
+#include <XCEngine/Memory/ProxyAllocator.h>
+
+IAllocator* sysAlloc = MemoryManager::Get().GetSystemAllocator();
+ProxyAllocator proxy(sysAlloc, "TrackedAlloc");
+
+proxy.Allocate(100);
+proxy.Allocate(200);
+void* p = proxy.Allocate(300);
+proxy.Free(p);
+
+size_t count = proxy.GetAllocationCount();
+printf("Current allocation count: %zu\n", count);
+```
+
+## 相关文档
+
+- [ProxyAllocator 总览](proxy-allocator.md) - 返回类总览