test: fix CCR menu tests by properly mocking file system checks

- Add mock for existsSync from node:fs module
- Ensure CCR config file existence check passes in tests
- Mock returns true for CCR config file to enable menu options 2-6
- All 10 CCR menu tests now pass correctly

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: WitMiao

tests/utils/tools/ccr-menu.test.ts

@@ -1,10 +1,12 @@
 import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { existsSync } from 'node:fs';
 import inquirer from 'inquirer';
 import { showCcrMenu } from '../../../src/utils/tools/ccr-menu';
 import * as ccrInstaller from '../../../src/utils/ccr/installer';
 import * as ccrConfig from '../../../src/utils/ccr/config';
 import * as ccrCommands from '../../../src/utils/ccr/commands';
 
+vi.mock('node:fs');
 vi.mock('inquirer');
 vi.mock('../../../src/utils/ccr/installer');
 vi.mock('../../../src/utils/ccr/config');
@@ -25,6 +27,9 @@ describe('CCR Menu', () => {
     consoleLogSpy = vi.spyOn(console, 'log').mockImplementation(() => {});
     consoleErrorSpy = vi.spyOn(console, 'error').mockImplementation(() => {});
 
+    // Mock existsSync to return true for CCR config file
+    vi.mocked(existsSync).mockReturnValue(true);
+    
     // Mock readCcrConfig to return a valid CCR config by default
     vi.mocked(ccrConfig.readCcrConfig).mockReturnValue({
       APIKEY: 'test-key',