feat: 实现D3D12 RHI抽象层，修复PSO创建问题

- 添加RHI接口定义(IRHIDevice, ICommandList, IResource等)
- 实现D3D12Device, D3D12CommandList, D3D12PipelineState等
- 修复RootSignature参数数量(3->4)与HelloEarth一致
- 修复DSV格式设置(Unknown->D24_UNorm_S8_UInt)
- 添加Geometry Shader编译
- 创建XCEngineDemo项目验证RHI功能

engine/src/RHI/D3D12/D3D12StaticMeshComponent.cpp

@@ -0,0 +1,86 @@
+#include <Rendering\StaticMeshComponent.h>
+#include <RHI\D3D12\D3D12Resources.h>
+#include <cstdio>
+
+namespace XCEngine {
+namespace RHI {
+
+StaticMeshComponent::StaticMeshComponent() {
+}
+
+StaticMeshComponent::~StaticMeshComponent() {
+    if (m_vertexBuffer) {
+        delete m_vertexBuffer;
+    }
+    for (auto& pair : m_subMeshes) {
+        delete pair.second;
+    }
+}
+
+bool StaticMeshComponent::Initialize(ICommandList* commandList, const char* filePath) {
+    FILE* file = nullptr;
+    if (fopen_s(&file, filePath, "rb") != 0) {
+        return false;
+    }
+    
+    int vertexCount = 0;
+    fread(&vertexCount, 4, 1, file);
+    m_vertexCount = vertexCount;
+    
+    MeshVertex* vertices = new MeshVertex[vertexCount];
+    fread(vertices, sizeof(MeshVertex), vertexCount, file);
+    
+    D3D12Device* device = nullptr;
+    
+    CreateVertexBuffer(device, commandList, vertices, sizeof(MeshVertex) * vertexCount, sizeof(MeshVertex), &m_vertexBuffer);
+    
+    delete[] vertices;
+    
+    while (!feof(file)) {
+        int nameLength = 0;
+        fread(&nameLength, 4, 1, file);
+        if (feof(file)) break;
+        
+        char name[256] = {0};
+        fread(name, 1, nameLength, file);
+        
+        int indexCount = 0;
+        fread(&indexCount, 4, 1, file);
+        
+        uint32_t* indices = new uint32_t[indexCount];
+        fread(indices, sizeof(uint32_t), indexCount, file);
+        
+        IIndexBuffer* indexBuffer = nullptr;
+        CreateIndexBuffer(device, commandList, indices, sizeof(uint32_t) * indexCount, &indexBuffer);
+        
+        delete[] indices;
+        
+        SubMesh* submesh = new SubMesh();
+        submesh->indexBuffer = indexBuffer;
+        submesh->indexCount = indexCount;
+        m_subMeshes[std::string(name)] = submesh;
+    }
+    
+    fclose(file);
+    return true;
+}
+
+void StaticMeshComponent::Render(ICommandList* commandList) {
+    if (!m_vertexBuffer) return;
+    
+    commandList->SetVertexBuffer(0, m_vertexBuffer, 0, sizeof(MeshVertex));
+    
+    if (m_subMeshes.empty()) {
+        commandList->DrawInstanced(m_vertexCount, 1, 0, 0);
+    }
+    else {
+        for (auto& pair : m_subMeshes) {
+            SubMesh* submesh = pair.second;
+            commandList->SetIndexBuffer(submesh->indexBuffer, 0);
+            commandList->DrawIndexedInstanced(submesh->indexCount, 1, 0, 0, 0);
+        }
+    }
+}
+
+} // namespace RHI
+} // namespace XCEngine