CLI help and docs name commands that don't exist ('ccas use', 'ccas manage|unmanage|managed')

[Sootopolis]

The --club option help on every slug-taking command points users at a command that was never registered.

CliCommand.scala:159 and :163:

"Club slug (URL name); falls back to the current club (set with 'ccas use')"

The registered name is use-club (CliCommand.scala:196). ClubResolver.scala:18 already has the correct wording — copy it.

Other stale names:

• README.md:70 command inventory lists use (four other README passages correctly say use-club).
• ManagedClubApp.scala:11 scaladoc names ccas manage|unmanage|managed — three commands that never shipped; the real surface is ccas club add|remove|list.

Also fold in the club group discoverability gap: ccas club --help lists add/remove/list with no pointer to setting a working club, and ccas --help renders use-club and club as unrelated siblings. Extend the group help at CliCommand.scala:359 and mirror at CompletionSpec.scala:118.

[Sootopolis]

Shipped in #183, squash-merged as a318e26.