fix: recognize arrow function beforeEach() hooks

[maks-oleksyuk]

Problem

PestHookPropertyReader infers $this->prop types by parsing the beforeEach() hook body for $this->prop = ... assignments — but it only recognized a real Closure (function () {}) as the hook argument. Writing the hook as an ArrowFunction (fn () => ...), a common Pest idiom for one-line setup, was silently skipped: every $this->prop read anywhere in the file fell back to mixed, with no PHPStan diagnostic to flag it.

Fix

Both places that gate on the hook argument's type (extractUsesBeforeEachProperties for pest()->beforeEach()->in(), and parseTestFile for the bare beforeEach() function) now accept Closure|ArrowFunction.

Property extraction was generalized to read from getStmts() instead of ->stmts directly: PhpParser's ArrowFunction::getStmts() wraps its single expression body in a synthetic Return_, so the extractor now matches Assign out of either an Expression (closure body) or a Return_ (arrow function body).

Testing

• 3 new assertType cases in tests/Type/data/test-hook-properties.php: object assignment, string literal assignment, and a non-assignment arrow body correctly staying mixed.
• 2 new cases in PestHookPropertyScopeTest.php (+ ArrowScoped fixture) proving the pest()->extend(...)->beforeEach(fn () => ...)->in(...) directory-scoped path also resolves and doesn't leak into sibling directories.
• pest --parallel: 468 passed. phpstan analyse: no errors. pint --test: clean.