Refactor Rector tooling for current stable releases

[mesilov]

Problem

During the 3.5.0 release PR, a fresh CI dependency install resolved rector/rector to 2.6.4 and phpstan/phpstan to 2.2.10. The current rector.php configuration still uses PHPUnitSetList::PHPUNIT_110, which is not available in Rector 2.6.x. Rector 2.5.2 also depends on PHPStan internals that changed in later PHPStan 2.2.x releases.

The release PR pins the current toolchain to the last verified stable combination: rector/rector 2.5.2 and phpstan/phpstan 2.2.2. This issue tracks upgrading that tooling separately.

Proposed solution

Update the Rector configuration to use the current supported PHPUnit set API, then relax the Composer constraints for Rector and PHPStan to current stable compatible releases.

Acceptance criteria

• rector.php no longer depends on removed versioned PHPUnit set constants such as PHPUnitSetList::PHPUNIT_110
• composer.json allows the current stable compatible versions of rector/rector and phpstan/phpstan
• A clean make composer-install resolves the tooling without manual dependency overrides
• make lint-rector passes
• make lint-phpstan passes
• The PR documents the release or maintenance decision in CHANGELOG.md when applicable