Experimenting with more structured ways to handle command-line input/output in Rust

Replace `proc-macro-error` with `proc-macro-error2`

Replaced with a fork as the original appears unmaintained.

Created by  finchie  on April 15, 2025
LYZBTYIWMOD3YTMOTBJBRNVYR7JOKVVGSHCFALKLGJO3IXTJC6HQC
Change contents