How to go from count of milliseconds since epoch into a sys-time?

[DavisVaughan]

If you're given 1762527600000, which is "2025-11-07 10:00:00 EST" but in milliseconds, how to convert to a millisecond precision sys-time?

Can't go through duration_milliseconds() because it requires integers and that is >integer.max

Don't want to blindly allow doubles everywhere because they can be fractional, and because large double whole numbers are not precisely represented.

Maybe could add duration_parse(x, precision =) that takes a character x and parses it into an int64_t at C level and stores it at the requested precision. Then you can as_sys_time() that.