chore: scaffold @insignia/iios-messaging-ui with jsdom test setup

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

packages/iios-messaging-ui/src/index.ts

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+export {};

packages/iios-messaging-ui/src/smoke.test.tsx

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+import { describe, it, expect } from 'vitest';
+import { render, screen } from '@testing-library/react';
+
+describe('test infrastructure', () => {
+  it('renders React components in jsdom', () => {
+    render(<div>messaging-ui</div>);
+    expect(screen.getByText('messaging-ui')).toBeDefined();
+  });
+});

packages/iios-messaging-ui/src/test-setup.ts

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+import { afterEach } from 'vitest';
+import { cleanup } from '@testing-library/react';
+
+// @testing-library/react auto-registers cleanup only when afterEach is a global.
+// We run with globals: false, so register it explicitly.
+afterEach(() => {
+  cleanup();
+});