fix: PHPStan and test strictness improvements

Add bin/ scripts to PHPStan scanFiles, suppress property.onlyWritten for
by-ref test properties, add exhaustive default match arm, use explicit
expects() on mock stubs, fix data provider return type, and simplify
redundant null check in NotificationServiceTest.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/Architecture/ModuleI18nContractTest.php

@@ -42,7 +42,7 @@ class ModuleI18nContractTest extends TestCase
             $modules[$moduleId] = [$moduleId, $resolvedPath];
         }
 
-        return $modules;
+        return array_values($modules);
     }
 
     #[DataProvider('moduleProvider')]