feat(Domain): add allowEmpty constructor option

[Copilot]

Domain::isValid() unconditionally rejected empty strings. This adds an opt-in allowEmpty flag (default false) that permits empty strings while still rejecting null and all other invalid values.

Changes

• Domain.php — added bool $allowEmpty = false as third constructor parameter; early-returns true for '' when the flag is set, using strict equality so null is not implicitly allowed
• DomainTest.php — added testAllowEmpty() covering default rejection, opt-in acceptance of '', continued rejection of null, and that normal valid/invalid domain rules are unaffected

Usage

$validator = new Domain(restrictions: [], hostnames: true, allowEmpty: true);

$validator->isValid('');            // true
$validator->isValid(null);          // false
$validator->isValid('example.com'); // true

Follows the same pattern already established in the URL validator.

[greptile-apps]

Greptile Summary

This PR adds an opt-in allowEmpty constructor flag to Domain that lets callers accept an empty string while still rejecting null, false, and all other invalid values. The implementation is minimal and correct: strict === equality prevents any PHP type-coercion widening, the early-return is placed before the existing empty() guard, and the new test covers the key boundary conditions. The previously-reported parse error (testRestrictions() missing its function declaration) is resolved in this revision.

Confidence Score: 5/5

Safe to merge — no logic errors, security concerns, or regressions identified.

The change is a small, isolated, additive feature with correct strict-equality guards and a default of false that preserves existing behavior. All previously-flagged issues (parse error in DomainTest.php) appear resolved.

No files require special attention.

Important Files Changed

Filename	Overview
src/Validator/Domain.php	Added bool $allowEmpty = false constructor parameter and a strict-equality early-return for ''; logic is correct and null/false/0 are not implicitly widened.
tests/Validator/DomainTest.php	Added testAllowEmpty() covering default rejection, opt-in acceptance of '', rejection of null and integers, and valid/invalid domain rules; testRestrictions() declaration is intact (previously-reported parse error is resolved).

_{Reviews (2): Last reviewed commit: "Apply suggestions from code review" | Re-trigger Greptile}

[Meldiron]

@copilot I dont see your last fixes. are you sure you commited and pushed changes?