feat: tabbed About dialog with keyboard shortcuts reference

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/lib/components/AboutDialog.test.ts

@@ -0,0 +1,59 @@
+import { describe, it, expect, vi } from 'vitest';
+import { render, fireEvent } from '@testing-library/svelte';
+import AboutDialog from '$lib/components/AboutDialog.svelte';
+
+vi.mock('@tauri-apps/api/app', () => ({
+  getVersion: vi.fn().mockResolvedValue('0.2.1'),
+}));
+
+describe('AboutDialog', () => {
+  it('renders the About tab by default', () => {
+    const { getByText } = render(AboutDialog, {
+      props: { onClose: vi.fn() },
+    });
+    expect(getByText('GUI Video Clipper')).toBeTruthy();
+    expect(getByText('by cottongin')).toBeTruthy();
+  });
+
+  it('shows two tabs: About and Shortcuts', () => {
+    const { getByRole } = render(AboutDialog, {
+      props: { onClose: vi.fn() },
+    });
+    const tablist = getByRole('tablist');
+    expect(tablist).toBeTruthy();
+    expect(tablist.querySelectorAll('[role="tab"]')).toHaveLength(2);
+  });
+
+  it('switches to Shortcuts tab on click', async () => {
+    const { getByText, getAllByText } = render(AboutDialog, {
+      props: { onClose: vi.fn() },
+    });
+    const shortcutsTab = getByText('Shortcuts');
+    await fireEvent.click(shortcutsTab);
+
+    expect(getAllByText('Play / Pause').length).toBeGreaterThan(0);
+    expect(getByText('Toggle mode')).toBeTruthy();
+    expect(getByText('Player Mode')).toBeTruthy();
+    expect(getByText('Clipper Mode')).toBeTruthy();
+  });
+
+  it('switches back to About tab', async () => {
+    const { getByText, getByRole } = render(AboutDialog, {
+      props: { onClose: vi.fn() },
+    });
+    await fireEvent.click(getByRole('tab', { name: 'Shortcuts' }));
+    await fireEvent.click(getByRole('tab', { name: 'About' }));
+
+    expect(getByText('GUI Video Clipper')).toBeTruthy();
+    expect(getByText('by cottongin')).toBeTruthy();
+  });
+
+  it('calls onClose when Close button is clicked', async () => {
+    const onClose = vi.fn();
+    const { getByText } = render(AboutDialog, {
+      props: { onClose },
+    });
+    await fireEvent.click(getByText('Close'));
+    expect(onClose).toHaveBeenCalled();
+  });
+});