feat(renderer): ModalLayer shell (dispatches to 7 modal types)

tests/component/modals/ModalLayer.test.tsx

@@ -0,0 +1,32 @@
+import { describe, it, expect, beforeEach } from 'vitest';
+import { render, screen } from '@testing-library/react';
+import { ModalLayer } from '@/components/modals/ModalLayer';
+import { useAppStore } from '@/stores/app-store';
+
+describe('ModalLayer', () => {
+  beforeEach(() => {
+    localStorage.clear();
+    useAppStore.setState({ modal: { kind: null } } as any);
+  });
+
+  it('renders nothing when modal is null', () => {
+    const { container } = render(<ModalLayer />);
+    expect(container.firstChild).toBeNull();
+  });
+
+  it('renders AboutDialog when kind is "about"', () => {
+    useAppStore.getState().openModal('about');
+    render(<ModalLayer />);
+    expect(screen.getByRole('dialog')).toBeInTheDocument();
+  });
+
+  it('switches from about to settings when modal kind changes', () => {
+    useAppStore.getState().openModal('about');
+    const { rerender } = render(<ModalLayer />);
+    expect(screen.getByText(/about markdownconverter/i)).toBeInTheDocument();
+    useAppStore.getState().openModal('settings');
+    rerender(<ModalLayer />);
+    expect(screen.queryByText(/about markdownconverter/i)).not.toBeInTheDocument();
+    expect(screen.getByText(/settings/i)).toBeInTheDocument();
+  });
+});