excludingClosures
fun NepaliSelectableDates.excludingClosures(provider: NepaliEventProvider): NepaliSelectableDates(source)
Returns a NepaliSelectableDates that delegates to this one but additionally rejects any date provider says the institution is shut for.
An event that does not close, a programme or a meeting, leaves its day selectable: the day is still worked, and refusing it would surprise anyone booking on it.
Year-level rejection still defers to the wrapped predicate, since event data is per-date.