D3D12: Fix Quad test screenshot and update texture

- Fix SetGraphicsRootDescriptorTable call order (SetRootSignature before SetPipelineState)
- Rename texture earth_d.jpg -> earth.png
- Fix vertex order for TriangleStrip quad rendering
- Add integration test README
- Add debug logging to D3D12Screenshot
- Remove obsolete run.bat

tests/RHI/D3D12/integration/README.md

@@ -0,0 +1,36 @@
+# D3D12 Integration Tests
+
+## minimal
+**后端**: D3D12Device, DXGIFactory, CommandQueue, CommandList, SwapChain
+**内容**: 最小 D3D12 初始化流程，创建窗口和交换链，无渲染输出
+
+---
+
+## triangle
+**后端**: D3D12Device, DXGIFactory, CommandQueue, CommandList, SwapChain, Buffer, Shader, RootSignature, PipelineState, RenderTargetView, DepthStencilView, Screenshot
+**内容**: 
+- 基础三角形渲染
+- 顶点 buffer 上传
+- HLSL shader 编译 (vs_5_1, ps_5_1)
+- Root signature + PSO 创建
+- RenderTarget 切换 (Present ↔ RenderTarget)
+- 截图功能验证
+
+---
+
+## quad
+**后端**: triangle 的全部 + Texture, DescriptorHeap, ShaderResourceView
+**内容**:
+- 四边形纹理采样渲染
+- Texture 加载与初始化 (stb_image)
+- DescriptorHeap (CBV_SRV_UAV) + SRV 创建
+- 静态采样器配置
+- Root signature descriptor table
+- SetDescriptorHeaps + SetGraphicsRootDescriptorTable
+- 截图功能验证
+
+---
+
+## render_model
+**后端**: (TODO)
+**内容**: 模型渲染 (待实现)