Title a collapsed Variables or Properties node by what it does

Collapsed, the node reads "Set 2 variables", "Get width" or "No properties";
expanded it is always "Variables" / "Properties". The Properties node shows
its object type (and behavior) as a line under the title instead.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/core/graph/nested.ts

@@ -51,6 +51,17 @@ export function declaredOn(
   return def.declaresPorts === side ? [...ports] : [];
 }
 
+/** What a collapsed Variables or Properties node does, since its ports are out of sight. */
+export function collapsedTitle(ports: readonly DeclaredPort[], noun: string): string {
+  const set = ports.filter((p) => p.write);
+  const get = ports.filter((p) => !p.write);
+  if (set.length > 1) return `Set ${set.length} ${noun}`;
+  if (get.length > 1) return `Get ${get.length} ${noun}`;
+  if (set[0]) return `Set ${set[0].key}`;
+  if (get[0]) return `Get ${get[0].key}`;
+  return `No ${noun}`;
+}
+
 /** The single start (or end) node of a graph; a second one is ignored. */
 export function terminalNode(graph: Graph, type: string): GraphNode | undefined {
   return graph.nodes.find((n) => n.type === type);