Fix Windows CI EPERM error in AJV schema validation cache

Problem

The Windows CI runner was failing intermittently with:

EPERM: operation not permitted, rename 'C:\a\serverless\serverless\packages\sf-core\sls-ajvqlvHza...' -> 'C:\Users\runneradmin.serverless\artifacts\ajv-validate-...'

Root Cause

The fsp.mkdtemp('sls-ajv') call in resolve-ajv-validate.js was creating temporary directories in the current working directory instead of the system temp directory.

On Windows CI:

• Source: C:\a\serverless\...\sls-ajvXXX\ (project workspace)
• Dest: C:\Users\runneradmin\.serverless\... (user home)

These are in different permission zones, causing EPERM errors during the atomic rename operation due to permission restrictions or file handle timing issues.

Solution

Changed mkdtemp to use the proper system temp directory:

// Before
const tmpDir = await fsp.mkdtemp('sls-ajv')

// After
const tmpDir = await fsp.mkdtemp(path.join(os.tmpdir(), 'sls-ajv'))