Grep scripts, aliases and README before deleting a helper script

When removing a helper shell script from a NixOS/home-manager flake repo, grep the whole repo (excluding .git) for its name first. Shell aliases often live in a different module from the script (e.g. a standalone home-manager module rather than the shared fish module), and the README may document it as a step. Delete the script with git rm, drop the alias, rewrite the README step, then re-grep to confirm zero references remain.