Suppress psalm ImplicitToStringCast in from()

Encoders accept string|Element in from() by design, but the Iso
generic is typed as Iso<mixed, string>.

Author: veewee

src/Encoder/XsiTypeEncoder.php

@@ -64,6 +64,7 @@ private function from(Context $context, Iso $innerIso, Element $value): mixed
                 ->unwrapOr($innerIso),
         };
 
+        /** @psalm-suppress ImplicitToStringCast - Encoders accept string|Element in from() */
         return $iso->from($value);
     }
 }