fix: preserve hidden tool visibility

src/App.test.tsx

@@ -124,6 +124,34 @@ describe('portal UI', () => {
     ).not.toBeInTheDocument();
   });
 
+  it('keeps remaining hidden tools visible while editing the hidden set', async () => {
+    vi.stubGlobal('fetch', vi.fn(catalogueFetch()));
+    const user = userEvent.setup();
+    render(<App />);
+    await screen.findByRole('heading', { name: 'PDF Workbench' });
+
+    await user.click(
+      screen.getByRole('button', { name: 'Hide PDF Workbench' })
+    );
+    const showHidden = screen.getByRole('checkbox', {
+      name: 'Show hidden (1)',
+    });
+    await user.click(showHidden);
+    await user.click(
+      screen.getByRole('button', { name: 'Hide XSLT Workbench' })
+    );
+    expect(showHidden).toHaveAccessibleName('Show hidden (2)');
+    await user.click(
+      screen.getByRole('button', { name: 'Show PDF Workbench' })
+    );
+
+    expect(showHidden).toBeChecked();
+    expect(showHidden).toHaveAccessibleName('Show hidden (1)');
+    expect(
+      screen.getByRole('heading', { name: 'XSLT Workbench' })
+    ).toBeInTheDocument();
+  });
+
   it('clears search filters without revealing hidden tools', async () => {
     vi.stubGlobal('fetch', vi.fn(catalogueFetch()));
     const user = userEvent.setup();