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

EngineTest/TestRenderer.cpp

@@ -0,0 +1,111 @@
+/**
+ * @file TestRenderer.cpp
+ * @brief 渲染功能综合测试实现。
+ */
+
+#include "TestRenderer.h"
+#include "Graphics/Renderer.h"
+#include "Platform/Platform.h"
+#include "Platform/PlatformTypes.h"
+#include <filesystem>
+#include <fstream>
+
+
+#if TEST_RENDERER
+using namespace XEngine;
+
+graphics::render_surface _surfaces[4];
+
+LRESULT win_proc(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam)
+{
+	bool toggle_fullscreen{ false };
+	switch (msg)
+	{
+	case WM_DESTROY:
+	{
+		bool all_closed{ true };
+		for (u32 i{ 0 }; i < _countof(_surfaces); ++i)
+		{
+			if(!_surfaces[i].window.is_closed())
+			{
+				all_closed = false;
+			}
+		}
+		if (all_closed)
+		{
+			PostQuitMessage(0);
+			return 0;
+		}
+		break;
+	}
+	case WM_SYSCHAR:
+	{
+
+		if(wparam == VK_RETURN && (HIWORD(lparam) & KF_ALTDOWN))
+		{
+			platform::window win{ platform::window_id{(id::id_type)GetWindowLongPtr(hwnd, GWLP_USERDATA)} };
+			win.set_fullscreen(!win.is_fullscreen());
+			return 0;
+		}
+		break;	
+	}
+
+}
+
+	return DefWindowProc(hwnd, msg, wparam, lparam);
+}
+
+void 
+create_render_surface(graphics::render_surface& surface, const platform::window_init_info info)
+{
+	surface.window = platform::create_window(&info);
+}
+
+void
+_destroy_render_surface(graphics::render_surface& surface)
+{
+	platform::remove_window(surface.window.get_id());
+}
+
+bool
+engine_test::initialize()
+{
+	bool result{ graphics::initialize(graphics::graphics_platform::direct3d12) };
+	if (!result)
+	{
+		return result;
+	}
+	platform::window_init_info info[]
+	{
+		{&win_proc, nullptr, L"Test Window 1", 200, 100,400,400},
+		{&win_proc, nullptr, L"Test Window 2", 700, 100,400,400},
+		{&win_proc, nullptr, L"Test Window 2", 700, 100,400,400},
+		{&win_proc, nullptr, L"Test Window 3", 1200,100,400,400},
+	};
+	static_assert(_countof(info) == _countof(_surfaces));
+	for (u32 i{ 0 }; i < _countof(_surfaces); ++i)
+	{
+		create_render_surface(_surfaces[i], info[i]);
+	}
+	return result;
+}
+
+void
+engine_test::run()
+{
+	std::this_thread::sleep_for(std::chrono::milliseconds(10));
+}
+
+bool
+engine_test::shutdown()
+{
+	for (u32 i{ 0 }; i < _countof(_surfaces); ++i)
+	{
+		_destroy_render_surface(_surfaces[i]);
+	}
+
+	graphics::shutdown();
+
+	return true;
+}
+#endif

EngineTest/TestRenderer.h

@@ -0,0 +1,15 @@
+/**
+ * @file TestRenderer.h
+ * @brief 渲染测试用例类声明。
+ */
+#pragma once
+#include "Test.h"
+
+
+class engine_test : public Test
+{
+public :
+	bool initialize() override;
+	void run() override;
+	bool shutdown() override;
+};