test(frontend): add comprehensive test coverage for Phase 3

- Add AI component tests (ContextConfigEditor, PromptEditor, RuntimeParametersPanel, SandboxTabs, VersionHistory)
- Add layout component tests (GlobalSearch, NotificationsDropdown, ProjectSwitcher, Sidebar, UserMenu)
- Update vitest.setup.ts for better test configuration
- Update .gitignore to exclude test artifacts
- All 722 tests passing

frontend/components/layout/__tests__/user-menu.test.tsx

@@ -0,0 +1,71 @@
+// File: frontend/components/layout/__tests__/user-menu.test.tsx
+// Change Log:
+// - 2026-06-14: สร้างใหม่สำหรับ Phase 3 Coverage
+
+import { render, screen } from '@testing-library/react';
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { UserMenu } from '../user-menu';
+
+// Mock next-auth
+vi.mock('next-auth/react', () => ({
+  useSession: vi.fn(),
+  signOut: vi.fn(),
+}));
+
+import { useSession } from 'next-auth/react';
+
+// Mock next/navigation
+vi.mock('next/navigation', () => ({
+  useRouter: vi.fn(),
+}));
+
+import { useRouter } from 'next/navigation';
+
+describe('UserMenu', () => {
+  const mockPush = vi.fn();
+
+  beforeEach(() => {
+    vi.clearAllMocks();
+    vi.mocked(useRouter).mockReturnValue({ push: mockPush });
+  });
+
+  it('ควร return null เมื่อไม่มี user', () => {
+    vi.mocked(useSession).mockReturnValue({ data: null });
+
+    const { container } = render(<UserMenu />);
+    expect(container.firstChild).toBeNull();
+  });
+
+  it('ควร render user menu เมื่อมี user', () => {
+    vi.mocked(useSession).mockReturnValue({
+      data: {
+        user: {
+          name: 'Test User',
+          email: 'test@example.com',
+          role: 'USER',
+        },
+      },
+    });
+
+    render(<UserMenu />);
+
+    const menuButton = screen.getByRole('button');
+    expect(menuButton).toBeInTheDocument();
+  });
+
+  it('ควรแสดง initials จากชื่อ user', () => {
+    vi.mocked(useSession).mockReturnValue({
+      data: {
+        user: {
+          name: 'Test User',
+          email: 'test@example.com',
+          role: 'USER',
+        },
+      },
+    });
+
+    render(<UserMenu />);
+
+    expect(screen.getByText('TU')).toBeInTheDocument();
+  });
+});