Release 3.2.8 PHP 8.4 nullable fix

[arm092]

Summary

• declare the optional sort direction as explicitly nullable
• remove the visible PHP 8.4 deprecation emitted when loading LivewireDatatable
• document the patch in the 3.2.8 changelog

Verification

• PHP 8.4 E_ALL class-load probe – no deprecations
• full src scan – no remaining implicit-nullable method parameters
• composer test -- --do-not-cache-result – 83 tests, 326 assertions

pm run test:browser – 2 passed

• composer audit --locked – no advisories

pm audit --audit-level=high – no vulnerabilities

• composer validate --strict – valid