Test case: ```js new Temporal.PlainDate(2025, 1, 1, "gregory").withCalendar("01").calendarId ``` Expected: Return the string `"iso8601"`. Actual: Throws a RangeError. [ParseTemporalCalendarString](https://tc39.es/proposal-temporal/#sec-temporal-parsetemporalcalendarstring), step 2.b defaults to using `"iso8601"` when no calendar is present in the input string.