Implement Comprehensive Test Suite for All Custom Sniffs

The package currently has zero functional tests for its 17 custom sniffs, creating a critical reliability risk. This is the highest priority issue that must be addressed before any production adoption.

Acceptance Criteria:

• Create test fixtures for all 17 custom sniffs
• Implement unit tests validating each sniff's detection logic
• Add integration tests for ruleset configurations
• Achieve minimum 90% test coverage for sniff code
• Remove placeholder tests (ExampleTest.php, Unit/ExampleTest.php)
• Document testing approach and conventions

Related Files:

• tests/Feature/ExampleTest.php (replace)
• tests/Unit/ExampleTest.php (replace)
• All sniff files in src/ArtisanPackUI/Sniffs/

Dependencies: None