Migrate sequentialthinking and filesystem servers from Jest to Vitest

- Replace Jest dependencies with Vitest and @vitest/coverage-v8
- Update test scripts to use 'vitest run --coverage'
- Create vitest.config.ts for both servers with node environment and coverage settings
- Update all test files:
  - Change imports from '@jest/globals' to 'vitest'
  - Replace jest.mock() with vi.mock()
  - Replace jest.fn() with vi.fn()
  - Update mock clearing/restoring to use vi methods
- Remove jest.config.cjs files
- All 151 tests passing (24 in sequentialthinking, 127 in filesystem)

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

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

src/filesystem/__tests__/directory-tree.test.ts

@@ -1,4 +1,4 @@
-import { describe, it, expect, beforeEach, afterEach } from '@jest/globals';
+import { describe, it, expect, beforeEach, afterEach } from 'vitest';
 import * as fs from 'fs/promises';
 import * as path from 'path';
 import * as os from 'os';

src/filesystem/__tests__/lib.test.ts

@@ -1,4 +1,4 @@
-import { describe, it, expect, beforeEach, afterEach, jest } from '@jest/globals';
+import { describe, it, expect, beforeEach, afterEach, vi } from 'vitest';
 import fs from 'fs/promises';
 import path from 'path';
 import os from 'os';
@@ -23,19 +23,19 @@ import {
 } from '../lib.js';
 
 // Mock fs module
-jest.mock('fs/promises');
-const mockFs = fs as jest.Mocked<typeof fs>;
+vi.mock('fs/promises');
+const mockFs = fs as any;
 
 describe('Lib Functions', () => {
   beforeEach(() => {
-    jest.clearAllMocks();
+    vi.clearAllMocks();
     // Set up allowed directories for tests
     const allowedDirs = process.platform === 'win32' ? ['C:\\Users\\test', 'C:\\temp', 'C:\\allowed'] : ['/home/user', '/tmp', '/allowed'];
     setAllowedDirectories(allowedDirs);
   });
 
   afterEach(() => {
-    jest.restoreAllMocks();
+    vi.restoreAllMocks();
     // Clear allowed directories after tests
     setAllowedDirectories([]);
   });
@@ -567,8 +567,8 @@ describe('Lib Functions', () => {
         
         // Mock file handle with proper typing
         const mockFileHandle = {
-          read: jest.fn(),
-          close: jest.fn()
+          read: vi.fn(),
+          close: vi.fn()
         } as any;
         
         mockFileHandle.read.mockResolvedValue({ bytesRead: 0 });
@@ -586,8 +586,8 @@ describe('Lib Functions', () => {
         mockFs.stat.mockResolvedValue({ size: 50 } as any);
         
         const mockFileHandle = {
-          read: jest.fn(),
-          close: jest.fn()
+          read: vi.fn(),
+          close: vi.fn()
         } as any;
         
         // Simulate reading file content in chunks
@@ -607,8 +607,8 @@ describe('Lib Functions', () => {
         mockFs.stat.mockResolvedValue({ size: 100 } as any);
         
         const mockFileHandle = {
-          read: jest.fn(),
-          close: jest.fn()
+          read: vi.fn(),
+          close: vi.fn()
         } as any;
         
         mockFileHandle.read.mockResolvedValue({ bytesRead: 0 });
@@ -626,8 +626,8 @@ describe('Lib Functions', () => {
       it('opens file for reading', async () => {
         // Mock file handle with proper typing
         const mockFileHandle = {
-          read: jest.fn(),
-          close: jest.fn()
+          read: vi.fn(),
+          close: vi.fn()
         } as any;
         
         mockFileHandle.read.mockResolvedValue({ bytesRead: 0 });
@@ -642,8 +642,8 @@ describe('Lib Functions', () => {
 
       it('handles files with content and returns first lines', async () => {
         const mockFileHandle = {
-          read: jest.fn(),
-          close: jest.fn()
+          read: vi.fn(),
+          close: vi.fn()
         } as any;
         
         // Simulate reading file content with newlines
@@ -661,8 +661,8 @@ describe('Lib Functions', () => {
 
       it('handles files with leftover content', async () => {
         const mockFileHandle = {
-          read: jest.fn(),
-          close: jest.fn()
+          read: vi.fn(),
+          close: vi.fn()
         } as any;
         
         // Simulate reading file content without final newline
@@ -680,8 +680,8 @@ describe('Lib Functions', () => {
 
       it('handles reaching requested line count', async () => {
         const mockFileHandle = {
-          read: jest.fn(),
-          close: jest.fn()
+          read: vi.fn(),
+          close: vi.fn()
         } as any;
         
         // Simulate reading exactly the requested number of lines

src/filesystem/__tests__/path-utils.test.ts

@@ -1,4 +1,4 @@
-import { describe, it, expect } from '@jest/globals';
+import { describe, it, expect } from 'vitest';
 import { normalizePath, expandHome, convertToWindowsPath } from '../path-utils.js';
 
 describe('Path Utilities', () => {

src/filesystem/__tests__/path-validation.test.ts

@@ -1,4 +1,4 @@
-import { describe, it, expect, beforeEach, afterEach } from '@jest/globals';
+import { describe, it, expect, beforeEach, afterEach } from 'vitest';
 import * as path from 'path';
 import * as fs from 'fs/promises';
 import * as os from 'os';

src/filesystem/__tests__/roots-utils.test.ts

@@ -1,4 +1,4 @@
-import { describe, it, expect, beforeEach, afterEach } from '@jest/globals';
+import { describe, it, expect, beforeEach, afterEach } from 'vitest';
 import { getValidRootDirectories } from '../roots-utils.js';
 import { mkdtempSync, rmSync, mkdirSync, writeFileSync, realpathSync } from 'fs';
 import { tmpdir } from 'os';