fix(cli): --group takes a name, and operator pair says it takes none

Two ways the CLI misled someone attaching a second group to a node.

`meshbay-node operator pair --group grenet` accepted the flag and ignored
it: pairing is node-wide and always was. That invites exactly the wrong
reading — that a code belongs to a group, and that pairing had failed
because the group did not change. It now refuses the flag and says one
paired browser covers every group the node hosts.

`--group` also only ever accepted a UUID. A name went through untouched
and the daemon answered as though the group did not exist, which is not
what happened. It now resolves a name against node.toml, and when there
is no match it prints the groups there are, with their ids — the missing
half of the answer.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

0 files changed, 0 insertions, 0 deletions