refactor(test): use crypto.randomUUID for temp directories

Replace Date.now() + Math.random() patterns with Node.js built-in
crypto.randomUUID() for cleaner and more robust unique directory
generation in tests. Fixes race condition in CI where tests running
in parallel could share the same directory name.

Changes:
- test/unit/fs-sync.test.ts: Use randomUUID and sequential execution
- test/unit/dlx.test.ts: Use randomUUID for test DLX directory
- test/unit/utils/temp-file-helper.mts: Use randomUUID in createTempDir and withTempFile

Benefits:
- Fixes ENOENT errors in CI from parallel test interference
- More straightforward than Date.now() + random string concatenation
- Guaranteed uniqueness with standard UUID format
- Sequential execution prevents shared variable race conditions
- Cleaner, more readable code

Author: jdalton

test/unit/dlx.test.ts

@@ -10,6 +10,7 @@
  * Used by Socket CLI for pnpm dlx / npx-style package execution.
  */
 
+import { randomUUID } from 'node:crypto'
 import fs from 'node:fs'
 import os from 'node:os'
 import path from 'node:path'
@@ -45,7 +46,7 @@ describe.sequential('dlx', () => {
   beforeEach(async () => {
     // Save original env and create isolated test directory
     originalEnv = process.env.SOCKET_DLX_DIR
-    testDlxDir = path.join(os.tmpdir(), `socket-dlx-test-${Date.now()}`)
+    testDlxDir = path.join(os.tmpdir(), `socket-dlx-test-${randomUUID()}`)
     process.env.SOCKET_DLX_DIR = testDlxDir
 
     // Clean up any existing test artifacts

test/unit/fs-sync.test.ts

@@ -10,6 +10,7 @@
  * - readFileBinary() for reading binary files
  */
 
+import { randomUUID } from 'node:crypto'
 import {
   existsSync,
   mkdirSync,
@@ -30,11 +31,11 @@ import {
 } from '@socketsecurity/lib/fs'
 import { beforeEach, describe, expect, it, afterEach } from 'vitest'
 
-describe('fs - Sync Functions', () => {
+describe.sequential('fs - Sync Functions', () => {
   let testDir: string
 
   beforeEach(() => {
-    testDir = join(tmpdir(), `socket-lib-test-${Date.now()}`)
+    testDir = join(tmpdir(), `socket-lib-test-${randomUUID()}`)
     mkdirSync(testDir, { recursive: true })
   })
 

test/unit/utils/temp-file-helper.mts

@@ -2,6 +2,7 @@
  * @fileoverview Temporary file and directory utilities for tests.
  */
 
+import { randomUUID } from 'node:crypto'
 import { promises as fs } from 'node:fs'
 import os from 'node:os'
 import path from 'node:path'
@@ -69,7 +70,7 @@ export function mockHomeDir(homeDir: string): () => void {
  */
 export async function createTempDir(prefix: string): Promise<string> {
   const tempBaseDir = os.tmpdir()
-  const tempDirName = `${prefix}${Date.now()}-${Math.random().toString(36).slice(2)}`
+  const tempDirName = `${prefix}${randomUUID()}`
   const tempDir = path.join(tempBaseDir, tempDirName)
 
   await fs.mkdir(tempDir, { recursive: true })
@@ -130,7 +131,7 @@ export async function withTempFile(
   const { extension = '.txt', prefix = 'temp-file-' } = options
 
   const tempBaseDir = os.tmpdir()
-  const tempFileName = `${prefix}${Date.now()}-${Math.random().toString(36).slice(2)}${extension}`
+  const tempFileName = `${prefix}${randomUUID()}${extension}`
   const tempFile = path.join(tempBaseDir, tempFileName)
 
   await fs.writeFile(tempFile, content, 'utf8')