fix(test): add mock-driver tests for database services

- Add connected-path tests for mysql, sql-server, and postgresql using
  mocked drivers (mysql2/promise, mssql, pg) covering
  connect, query, transaction, and disconnect scenarios
- Fix tautological assertion in auth-flow.test.ts (hasError >= 0 was always true)
- Add tests/integration to vitest exclude list to prevent
  module cache pollution under isolate:false
- Set isolate to true for CI, false for local dev (was: isolate false)

vitest.config.ts

@@ -6,13 +6,13 @@ export default defineConfig({
     globals: true,
     environment: 'node',
     include: ['tests/**/*.{test,spec}.{ts,tsx}'],
-    exclude: ['node_modules', 'dist', 'out', 'tests/e2e'],
+    exclude: ['node_modules', 'dist', 'out', 'tests/e2e', 'tests/integration'],
     setupFiles: ['tests/setup.ts'],
     env: {
       NODE_ENV: 'test'
     },
-    // 性能优化配置
-    isolate: false, // 禁用隔离（提升 30-50% 速度）
+    // CI 环境启用隔离以捕获跨文件状态污染；本地开发禁用以提升速度
+    isolate: !!process.env.CI,
     pool: 'threads', // 使用线程池
     maxWorkers: 4,
     bail: process.env.CI ? 1 : undefined,