feat: add terminal panel components and Zustand store for state management

- Created a barrel export file for terminal panel components.
- Implemented Zustand store for managing terminal panel UI state, including visibility, active terminal, view mode, and terminal ordering.
- Added actions for opening/closing the terminal panel, setting the active terminal, changing view modes, and managing terminal order.
- Introduced selectors for accessing terminal panel state properties.

ccw/frontend/src/pages/CodexLensManagerPage.test.tsx

@@ -7,7 +7,6 @@ import { describe, it, expect, beforeEach, vi } from 'vitest';
 import { render, screen, waitFor } from '@/test/i18n';
 import userEvent from '@testing-library/user-event';
 import { CodexLensManagerPage } from './CodexLensManagerPage';
-import * as api from '@/lib/api';
 
 // Mock api module
 vi.mock('@/lib/api', () => ({