Run tests on PHP 8.5 and update test environment

[clue]

This changeset updates the test environment to run the test suite on PHP 8.5, which deprecates the setAccessible() calls used in our tests.

Builds on top of #24, #23, reactphp/stream#179, reactphp/event-loop#282, and clue/framework-x#297

[Copilot]

🟢 Approval recommended

The focused compatibility and environment updates have no identified blocking issues.

No open issues 🎉

What changed in this PR

Updates the test environment for PHP 8.5 while preserving compatibility with older PHP versions.

Changes:

• Adds PHP 8.5 to CI and updates the checkout action.
• Raises minimum ReactPHP dependency versions.
• Limits setAccessible() calls to PHP versions below 8.1.

File	Description
tests/​TarDecoderTest.php	Guards reflection calls to avoid PHP 8.5 deprecations.
composer.json	Updates stream and event-loop dependency requirements.
.github/​workflows/​ci.yml	Adds PHP 8.5 and updates checkout to v7.

_{Review effort: Balanced}