Add 500+ instance performance regression test

tests/perf-budget.test.js

@@ -59,3 +59,16 @@ test("compile remains under baseline perf budget for large synthetic model", ()
   assert.equal(typeof result.layout_metrics.overlap_edges, "number");
   assert.ok(elapsedMs < 5_000, `compile exceeded baseline budget: ${elapsedMs.toFixed(1)}ms`);
 });
+
+test("compile handles 500+ instances and 1000+ net nodes within budget", () => {
+  const model = createLargeModel(520);
+  const totalNodes = model.nets.reduce((sum, net) => sum + (net.nodes?.length ?? 0), 0);
+  const started = performance.now();
+  const result = compile(model);
+  const elapsedMs = performance.now() - started;
+
+  assert.equal(result.ok, true);
+  assert.ok(model.instances.length >= 500);
+  assert.ok(totalNodes >= 1000);
+  assert.ok(elapsedMs < 10_000, `compile exceeded large-scene budget: ${elapsedMs.toFixed(1)}ms`);
+});