fix(decode): decode into a defined string or bool type

Assisted-by: DeepSeek V4.1 Flash

decode.go

@@ -202,7 +202,10 @@ func setBasic(dst, val reflect.Value, kind string) error {
 	if dst.Kind() != val.Kind() {
 		return fmt.Errorf("interpres: cannot assign %s to %s", kind, dst.Type())
 	}
-	dst.Set(val)
+	// Convert rather than assign: a value of the predeclared type is not
+	// assignable to a defined type of the same kind, so a plain Set panics on
+	// a destination such as `type Name string`.
+	dst.Set(val.Convert(dst.Type()))
 	return nil
 }