fix: D3D12 CreateTexture defaults and CommandList RTV support

- Add default value handling for sampleCount, mipLevels, depth in CreateTexture
- Add RTV descriptor heap to D3D12CommandList for future ClearRenderTarget implementation
- ClearRenderTarget remains stub (requires full D3D12 render pipeline state)

engine/src/RHI/D3D12/D3D12CommandList.cpp

@@ -19,6 +19,7 @@ bool D3D12CommandList::Initialize(ID3D12Device* device, CommandQueueType type, I
     D3D12_COMMAND_LIST_TYPE listType = ToD3D12(type);
 
     m_commandAllocator = allocator;
+    m_device = device;
 
     HRESULT hResult = device->CreateCommandList(
         0,
@@ -34,11 +35,22 @@ bool D3D12CommandList::Initialize(ID3D12Device* device, CommandQueueType type, I
 
     m_type = type;
 
+    D3D12_DESCRIPTOR_HEAP_DESC heapDesc = {};
+    heapDesc.NumDescriptors = 16;
+    heapDesc.Type = D3D12_DESCRIPTOR_HEAP_TYPE_RTV;
+    heapDesc.Flags = D3D12_DESCRIPTOR_HEAP_FLAG_NONE;
+    heapDesc.NodeMask = 0;
+    hResult = device->CreateDescriptorHeap(&heapDesc, IID_PPV_ARGS(&m_rtvHeap));
+    if (FAILED(hResult)) {
+        return false;
+    }
+
     return true;
 }
 
 void D3D12CommandList::Shutdown() {
     m_commandList.Reset();
+    m_rtvHeap.Reset();
     m_resourceStateMap.clear();
     m_trackedResources.clear();
 }
@@ -312,8 +324,6 @@ void D3D12CommandList::DrawIndexedInstancedIndirectInternal(ID3D12Resource* argB
 }
 
 void D3D12CommandList::ClearRenderTargetView(ID3D12Resource* renderTarget, const float color[4], uint32_t rectCount, const D3D12_RECT* rects) {
-    D3D12_CPU_DESCRIPTOR_HANDLE rtvHandle = {};
-    m_commandList->ClearRenderTargetView(rtvHandle, color, rectCount, rects);
 }
 
 void D3D12CommandList::ClearRenderTargetView(D3D12_CPU_DESCRIPTOR_HANDLE renderTargetHandle, const float color[4], uint32_t rectCount, const D3D12_RECT* rects) {