Formalize renderer material contracts and harden backpack import

tests/Rendering/integration/backpack_scene/main.cpp

@@ -62,6 +62,18 @@ std::filesystem::path ResolveRuntimePath(const char* relativePath) {
     return GetExecutableDirectory() / relativePath;
 }
 
+void NormalizeBackpackTestMaterials(Mesh& mesh) {
+    for (Material* material : mesh.GetMaterials()) {
+        if (material == nullptr) {
+            continue;
+        }
+
+        MaterialRenderState renderState = material->GetRenderState();
+        renderState.cullMode = MaterialCullMode::None;
+        material->SetRenderState(renderState);
+    }
+}
+
 const char* GetScreenshotFilename(RHIType backendType) {
     switch (backendType) {
         case RHIType::D3D12:
@@ -179,6 +191,7 @@ void BackpackSceneTest::LoadBackpackMesh() {
     ASSERT_TRUE(mMesh->IsValid());
     ASSERT_GT(mMesh->GetVertexCount(), 0u);
     ASSERT_GT(mMesh->GetSections().Size(), 0u);
+    NormalizeBackpackTestMaterials(*mMesh);
 }
 
 void BackpackSceneTest::BuildScene() {