feat: titlebar icon for sidebar toggle first try

tests/renderer/components/WindowTitleBar.test.tsx

@@ -0,0 +1,38 @@
+import React from 'react';
+import { describe, it, expect, beforeEach } from 'vitest';
+import { fireEvent, render, screen } from '@testing-library/react';
+import { WindowTitleBar } from '../../../src/renderer/components/WindowTitleBar/WindowTitleBar';
+import { useAppStore } from '../../../src/renderer/store';
+
+describe('WindowTitleBar', () => {
+  beforeEach(() => {
+    useAppStore.setState({
+      sidebarVisible: true,
+    });
+  });
+
+  it('renders a right-side sidebar toggle button and toggles store state', () => {
+    render(<WindowTitleBar />);
+
+    const toggleButton = screen.getByLabelText('Toggle Sidebar');
+    expect(toggleButton).toBeInTheDocument();
+    expect(toggleButton).toHaveAttribute('title', 'Hide Sidebar (Ctrl+B)');
+
+    fireEvent.click(toggleButton);
+
+    expect(useAppStore.getState().sidebarVisible).toBe(false);
+    expect(toggleButton).toHaveAttribute('title', 'Show Sidebar (Ctrl+B)');
+  });
+
+  it('uses a VS Code-like sidebar toggle icon shape', () => {
+    render(<WindowTitleBar />);
+
+    const toggleButton = screen.getByLabelText('Toggle Sidebar');
+    const svg = toggleButton.querySelector('svg');
+    const paths = svg?.querySelectorAll('path');
+
+    expect(svg).not.toBeNull();
+    expect(paths?.[0]?.getAttribute('d')).toBe('M3 3.75A1.75 1.75 0 0 1 4.75 2h6.5A1.75 1.75 0 0 1 13 3.75v8.5A1.75 1.75 0 0 1 11.25 14h-6.5A1.75 1.75 0 0 1 3 12.25v-8.5z');
+    expect(paths?.[1]?.getAttribute('d')).toBe('M4.5 3.5h3.75v9H4.5z');
+  });
+});