"t initial" input field mishandles double-clicks

[lpgagnon]

https://discord.com/channels/319857228905447436/480397772248580098/1052773337211875368

Double-clicking digits in the t-initial field selects both digits and their unit, so typing deletes the unit along with the digits, and has to be retyped to pass validation

other time fields don't have this issue, presumably because they use a different formatting with a space between digits and unit