the crash when calling `nix help-stores` was probably introduced an
artifact from a prior untangling of merge conflicts.
that said, `nix help-stores` should eventually cease to exist in favor
of dedicated `--help` outputs and `man` pages for the various store
types.
the `term` output mode leaves inline HTML around verbatim, while `nroff`
mode (used for `man` pages) does not.
the correct solution would be to pre-render all output with a more
benign tool so we have less liabilities in our own code, but this has to
do for now.
