feat: add Graphics module with D3D12 backend and documentation

Graphics Module:
- Add platform abstraction layer (GraphicsPlatformInterface)
- Add unified renderer entry point (Renderer)
- Add D3D12 backend implementation (D3D12Core, D3D12Interface)
- Add TestRenderer for multi-window rendering tests

Documentation:
- Add Graphics渲染架构分析.md
- Add D3D12学习Wiki.md
- Add changelogs directory with per-commit documentation
- Add 20260326-dx12-initial.md for initial framework
- Add 20260326-d3d12-foundation.md for Graphics module

Fixes:
- Resolve header include issues and type redefinition errors

Engine/Graphics/Direct3D12/D3D12CommonHeader.h

@@ -0,0 +1,17 @@
+#pragma once
+
+#include "CommonHeader.h"
+#include "Graphics\Renderer.h"
+
+// 引入 DirectX Graphics Infrastructure（DXGI）6.0 
+// 头文件，用于访问 DXGI 接口（如 IDXGIFactory6、
+// IDXGIAdapter4 等），支持枚举 GPU、查询显示模式、管理
+// 交换链等底层图形功能
+#include <dxgi1_6.h>
+// 引入 Direct3D 12 头文件，提供 D3D12 API 接口，
+// 用于创建渲染管线、管理资源与 GPU 命令
+#include <d3d12.h>
+
+// 引入 Windows Runtime C++ 模板库（WRL）头文件，提供智能指针（如 Microsoft::WRL::ComPtr）
+// 用于简化 COM 对象的生命周期管理
+#include <wrl.h>

Engine/Graphics/Direct3D12/D3D12Core.cpp

@@ -0,0 +1,20 @@
+#include "D3D12Core.h"
+#include "D3D12CommonHeader.h"
+
+namespace XEngine::graphics::d3d12::core{
+namespace{
+
+ID3D12Device8* main_device;
+
+}// anonymous namespace
+bool 
+initialize()
+{
+    // determine which adapter
+	return true;
+}
+void 
+shutdown()
+{
+}
+}// namespace XEngine::graphics::d3d12::core

Engine/Graphics/Direct3D12/D3D12Core.h

@@ -0,0 +1,6 @@
+#pragma once
+
+namespace XEngine::graphics::d3d12::core{
+bool initialize();
+void shutdown();
+}// namespace XEngine::graphics::d3d12

Engine/Graphics/Direct3D12/D3D12Interface.cpp

@@ -0,0 +1,14 @@
+#include "D3D12Interface.h"
+#include "D3D12Core.h"
+#include "Graphics\GraphicsPlatformInterface.h"
+
+namespace XEngine::graphics::d3d12{
+void get_platform_interface(platform_interface& pi)
+{
+	pi.initialize = core::initialize;
+    pi.shutdown = core::shutdown;
+}
+}// namespace XEngine::graphics::d3d12
+
+
+

Engine/Graphics/Direct3D12/D3D12Interface.h

@@ -0,0 +1,9 @@
+#pragma once
+
+namespace XEngine::graphics{
+struct platform_interface;
+}
+
+namespace XEngine::graphics::d3d12{
+void get_platform_interface(platform_interface& gfx);
+}// namespace XEngine::graphics::d3d12