fix(frontend): sprint 5 post-code-review — dropdown close-on-outside + empty-state dropdown

- useEffect pointerdown + Escape listeners when dropdown open (NIT 1)
- empty state now renders NewSimulationDropdown instead of plain Link (NIT 2)
- 3 new Vitest: close-on-outside, close-on-Escape, empty-state has dropdown

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/tests/SimulationList.test.tsx

@@ -142,6 +142,44 @@ describe('SimulationList — admin/redteam', () => {
     });
   });
 
+  it('closes dropdown on click outside', async () => {
+    mock.onGet('/engagements/42/simulations').reply(200, SIMULATIONS);
+    const user = userEvent.setup();
+    renderWithProviders(<SimulationList engagementId={42} />);
+    await waitFor(() => {
+      expect(screen.getByText('Lateral movement test')).toBeInTheDocument();
+    });
+    await user.click(screen.getByTestId('new-simulation-dropdown-toggle'));
+    expect(screen.getByTestId('from-template-btn')).toBeInTheDocument();
+    // Click outside the dropdown
+    await user.click(document.body);
+    expect(screen.queryByTestId('from-template-btn')).toBeNull();
+  });
+
+  it('closes dropdown on Escape key', async () => {
+    mock.onGet('/engagements/42/simulations').reply(200, SIMULATIONS);
+    const user = userEvent.setup();
+    renderWithProviders(<SimulationList engagementId={42} />);
+    await waitFor(() => {
+      expect(screen.getByText('Lateral movement test')).toBeInTheDocument();
+    });
+    await user.click(screen.getByTestId('new-simulation-dropdown-toggle'));
+    expect(screen.getByTestId('from-template-btn')).toBeInTheDocument();
+    await user.keyboard('{Escape}');
+    expect(screen.queryByTestId('from-template-btn')).toBeNull();
+  });
+
+  it('shows dropdown in empty state (not a plain link)', async () => {
+    mock.onGet('/engagements/42/simulations').reply(200, []);
+    renderWithProviders(<SimulationList engagementId={42} />);
+    await waitFor(() => {
+      expect(screen.getByTestId('empty-state')).toBeInTheDocument();
+    });
+    // Must have the split-button dropdown, not a plain link
+    expect(screen.getByTestId('new-simulation-btn')).toBeInTheDocument();
+    expect(screen.getByTestId('new-simulation-dropdown-toggle')).toBeInTheDocument();
+  });
+
   it('clicking a row uses SPA navigation and does not trigger window.location change', async () => {
     mock.onGet('/engagements/42/simulations').reply(200, SIMULATIONS);
     const originalHref = window.location.href;