Fix sanitizeForUrl array handling for lowercase step

strtolower does not accept arrays; use array_map when result is an
array, consistent with the array_walk fix for the trim step.

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

Author: carlbennett

src/Libraries/Core/StringProcessor.php

@@ -43,7 +43,7 @@ public static function sanitizeForUrl(array|string $haystack, bool $lowercase =
         {
             \array_walk($result, fn(&$v) => $v = \trim($v, '-'));
         }
-        if ($lowercase) $result = \strtolower($result);
+        if ($lowercase) $result = \is_array($result) ? \array_map('\strtolower', $result) : \strtolower($result);
         return $result;
     }