feat: release design system engine, studio and component contracts

packages/test/src/index.ts

@@ -100,6 +100,8 @@ export function mountHtml(html: string): {
   const g = globalThis as Record<string, unknown>;
   g.window = win;
   g.document = win.document;
+  // Runtime-dispatched events must belong to the simulated browser, not Bun.
+  g.CustomEvent = win.CustomEvent;
   g.NodeFilter = win.NodeFilter;
   g.HTMLInputElement = win.HTMLInputElement;
   g.HTMLOptionElement = win.HTMLOptionElement;