docs: update memory and threading API docs

docs/api/threading/task-group/add-task.md

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+# TaskGroup::AddTask
+
+```cpp
+uint64_t AddTask(std::unique_ptr<ITask> task);
+uint64_t AddTask(Callback&& func, TaskPriority priority = TaskPriority::Normal);
+```
+
+将任务添加到任务组。支持两种添加方式：传入 ITask 对象或传入回调函数。
+
+**参数：**
+- `task` - 唯一指针管理的 ITask 对象
+- `func` - 要执行的回调函数
+- `priority` - 任务优先级，默认为 `TaskPriority::Normal`
+
+**返回：** 返回分配的任务 ID，可用于设置依赖关系
+
+**线程安全：** ✅ 线程安全
+
+**复杂度：** O(1)
+
+**示例：**
+
+```cpp
+#include "XCEngine/Threading/TaskGroup.h"
+#include "XCEngine/Threading/Task.h"
+#include <iostream>
+#include <memory>
+
+using namespace XCEngine::Threading;
+
+class MyTask : public ITask {
+public:
+    explicit MyTask(const std::string& name) : m_name(name) {}
+
+    void Execute() override {
+        std::cout << "Executing: " << m_name << "\n";
+    }
+
+private:
+    std::string m_name;
+};
+
+int main() {
+    TaskGroup group;
+
+    auto task = std::make_unique<MyTask>("DataLoading");
+    uint64_t taskId = group.AddTask(std::move(task));
+
+    uint64_t callbackId = group.AddTask([]() {
+        std::cout << "Lambda task executing\n";
+    }, TaskPriority::High);
+
+    group.AddDependency(callbackId, taskId);
+
+    group.Wait();
+    return 0;
+}
+```
+
+## 相关文档
+
+- [TaskGroup 总览](task-group.md) - 返回类总览