Cover the stored modification format with the demo artwork that leans on it

Author: Keavon

editor/src/messages/portfolio/document/storage_tests/round_trip_tests.rs

@@ -716,6 +716,38 @@ async fn demo_artwork_edit_autosaves_and_round_trips() {
 	editor.active_document_mut().commit_storage_snapshot(&byte_store, true);
 }
 
+/// Manual edits ride a saved document as a folded `VectorModification`, so opening the artworks carrying the most
+/// of them is what proves the stored format still reads and applies. Each layer edited through a Path node must
+/// surface anchors, which catches a single modification that deserialized into nothing.
+#[tokio::test]
+async fn demo_artwork_vector_modifications_still_apply() {
+	for name in ["red-dress", "isometric-fountain", "valley-of-spires"] {
+		let mut editor = EditorTestUtils::create();
+
+		let data = std::fs::read(format!("../demo-artwork/{name}.graphite")).expect("read demo artwork");
+		editor
+			.handle_message(IngestMessage::Ingest {
+				data,
+				action: IngestAction::Open,
+				mime_type: String::new(),
+				path: Some(format!("{name}.graphite").into()),
+			})
+			.await;
+
+		let document = editor.active_document();
+		let path_layers: Vec<_> = document
+			.metadata()
+			.all_layers()
+			.filter_map(|layer| Some((layer, document.network_interface.upstream_path_node_vector(layer)?)))
+			.collect();
+		assert!(!path_layers.is_empty(), "{name} has no layers edited through a Path node");
+
+		for (layer, geometry) in path_layers {
+			assert!(geometry.anchor_points().next().is_some(), "{name} layer {layer:?} surfaced no anchors from its stored modification");
+		}
+	}
+}
+
 /// The document's single Fill node, as `(network_path, node_id)`.
 fn find_fill_node(document: &DocumentMessageHandler) -> (Vec<graph_craft::document::NodeId>, graph_craft::document::NodeId) {
 	node_paths(&document.network_interface)