removed hard coded shader start up

tests/RenderCadenceCompositorRuntimeLayerModelTests.cpp

@@ -180,6 +180,22 @@ void TestRejectsUnsupportedStartupShader()
 	std::filesystem::remove_all(root);
 }
 
+void TestEmptyStartupShaderKeepsModelEmpty()
+{
+	std::filesystem::path root;
+	RenderCadenceCompositor::SupportedShaderCatalog catalog = MakeCatalog(root);
+
+	RenderCadenceCompositor::RuntimeLayerModel model;
+	std::string error = "unexpected";
+	Expect(model.InitializeSingleLayer(catalog, "", error), "empty startup shader is accepted");
+	Expect(error.empty(), "empty startup shader reports no error");
+	Expect(model.FirstLayerId().empty(), "empty startup shader creates no startup layer");
+	Expect(model.Snapshot().displayLayers.empty(), "empty startup shader leaves display model empty");
+	Expect(model.PendingLayerBuilds().empty(), "empty startup shader queues no build");
+
+	std::filesystem::remove_all(root);
+}
+
 void TestBuildFailureStaysDisplaySide()
 {
 	std::filesystem::path root;
@@ -576,6 +592,7 @@ int main()
 {
 	TestSingleLayerLifecycle();
 	TestRejectsUnsupportedStartupShader();
+	TestEmptyStartupShaderKeepsModelEmpty();
 	TestBuildFailureStaysDisplaySide();
 	TestAddAndRemoveLayers();
 	TestSnapshotCompileMessageSummarizesLayerStack();