I added a 01/01/2025 in column I.

Formula in C2 is this:

=LET(total, NETWORKDAYS.INTL(C$1, D$1 - 1, 1, ), start, MAX($A2, C$1), end, MIN($B2, D$1 - 1), IF(start > end, 0, NETWORKDAYS.INTL(start, end, 1, ) / total))

You can fill it to the right, then fill it down.