The endpoint landed inert: nothing pointed at it, so the only way to see
it work was to mint an HMAC by hand. Register the two swarm-wide hooks
at startup so a real forge event produces a journal line.
Registered ALONGSIDE the per-hive hooks, not instead of them. Every hive
keeps receiving and acting on its own deliveries; the controller gets a
copy and logs it. Moving the registration is a later step and has to be:
fan-out swarm->hive does not exist yet, so a hook moved now would point
at a receiver that forwards nowhere, silently on both sides.
Deliberately no stale-hook deletion arm, unlike the two per-hive
registrars this otherwise mirrors: theirs delete hooks matching their own
path with a foreign base, and the hives' hooks are not stale.
The route prefix is what keeps this safe. Both hive-side registrars
delete any hook ending in /webhook/knowledge or /webhook/config-pr with a
different base, so a swarm hook under those paths would be deleted by
every hive on every boot. Serving them under /webhook/forge/ avoids it,
and a test pins it -- there is nothing else that can.
SWARM_CONTROLLER_PUBLIC_URL is set only where the swarm vhost is served,
because a hook whose target_url nothing answers is worse than no hook.