- commands/list/list.sh: router + command::define show [*]
- commands/list/show.sh: flag::define + flag::parse, all helpers
- flag::exclusive: register under top-level command name (strip ::subcmd)
- flag::parse: validate exclusive groups, error on conflicting user flags
- --help: intercept in command::run before routing
- help::auto: don't show default subcommand in usage line