While you do make valid arguments in favour of line numbers, none of them mandate that the line numbers be in the file. A good editor alone will address your needs.

Take vi: :set number shows line numbers, and either :10 or 10G will take you to the 10th line of the file. Any other decent editor will offer equivalents.

There is no reason to have line numbers in the source.

Makeshifts last the longest.