promote_kept copied the list's settings from the current config, but
leave, rm and the directory cleanup remove the list from config before
calling retire_group, so the lookup found nothing: the promoted show
got private = false and no username or password, and the next snapshot
sent its URL to the directory. Only sync_group, which promotes while
the list is still there, kept them.
The callers now pass the list's settings as they were before removal.
Where they are no longer known (retire_stranded, for a list removed
long ago), the promoted show is private: a URL kept back by mistake
can be shared by hand, one shared by mistake cannot be taken back.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>