fix: 修复 D3D12SwapChain 重复创建 swapchain 问题

- 添加 Initialize(IDXGISwapChain*, width, height) 重载方法
- 接受已存在的 swapchain 而不是重复创建
- 测试通过，日志显示正常渲染

tests/D3D12/main.cpp

@@ -606,7 +606,7 @@ bool InitD3D12(HWND inHWND, int inWidth, int inHeight) {
 
 	IDXGISwapChain* swapChain = nullptr;
 	dxgiFactory->CreateSwapChain(gCommandQueue.GetCommandQueue(), &swapChainDesc, &swapChain);
-	gSwapChain.Initialize(dxgiFactory, gCommandQueue.GetCommandQueue(), inHWND, inWidth, inHeight, 2);
+	gSwapChain.Initialize(swapChain, inWidth, inHeight);
 
 	D3D12_HEAP_PROPERTIES d3dHeapProperties = {};
 	d3dHeapProperties.Type = D3D12_HEAP_TYPE_DEFAULT;