Per operator review: hivectl shouldn't make the operator retype this
hive's own domain. Add a HostRequest::HiveDomain admin-socket query
(c0re answers from HYPERHIVE_HIVE_DOMAIN, already in its service env) and
a domain field on HostResponse.
hivectl peer-config now resolves the domain as: --domain override (kept
for offline/scripted use), else the daemon query; errors with a clear
hint when neither resolves. wg init resolves it best-effort too, so it
prints the hand-over peer-config block without --domain (skipped, not
failed, when the daemon is unreachable).
Regenerated docs/tools/hivectl-cli.md.
72d9422a7a