The lark_*->channel_* cutover (MUL-3515) is deployed to prod, and the
MULTICA_LARK_HUB_DISABLED park-switch was a one-time scaffold for that
rollout — the end state intentionally does not use it (prod never set the
env). Remove the env-gated branch from cmd/server/main.go so the channel
supervisor always starts when built; its existing nil-guard and shutdown
join are unchanged. Trim migration 124's now-obsolete switch runbook to a
short historical note (comment-only; 124 is already applied, so this does
not re-run).
Refs MUL-3515
Co-authored-by: J <j@multica.ai>
Co-authored-by: multica-agent <github@multica.ai>
5e824a94ae