fix: skip Sequence validation for $tenant attribute

Tenant can be int or string depending on the adapter, so it should
not go through Sequence validation which is string-only. Tenant is
a framework-controlled internal attribute set via setTenant().

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: abnegate

src/Database/Validator/Structure.php

@@ -340,6 +340,9 @@ protected function checkForInvalidAttributeValues(array $structure, array $keys)
 
             switch ($type) {
                 case Database::VAR_ID:
+                    if ($attribute['$id'] === '$tenant') {
+                        break;
+                    }
                     $validators[] = new Sequence($this->idAttributeType, $attribute['$id'] === '$sequence');
                     break;