list ignored --help and listed parties; leave and status ignored stray
arguments; who silently kept the last of several positionals; log took
a positional name that neither its usage nor the man page documents.
All now follow the parser convention of the other subcommands: help on
-h, exit 2 on an unknown flag or unexpected argument.
tmux-party: share a tmux session with people on the same UNIX host.
Single-file POSIX shell (party) with a filesystem + tmux server-access
trust model. See README.md.
