ErrorMap

Passed as the errorMap option of struct.parse. It is called for each issue (code, expected, message, path, received) before the issue is recorded. Any string, including '', replaces the default message; only undefined keeps it. The map belongs to this parse call and also handles bigint/date conversion failures from a struct created by another Core copy. Default messages omit received values; custom text is used verbatim, so avoid including sensitive received values.