fix(pm-agent): the agent is IN the cluster — one git host, the cluster-local service name

An in-cluster consumer reaches a service by its *.svc.cluster.local name, which is by
design a different path from how a client outside the cluster reaches the same service.
pm-worker's host allowlist accepted TWO values: the cluster-local name and the external
hostname gitea.home.keithjackson.dev. The second is removed.

It was never needed — nothing sets it — it would route in-cluster traffic out through the
Gateway and back for no reason, and as an ACCEPTED value it widened the allowlist to a
host reachable over the namespace's world:443 egress rule, which is precisely the
injection shape the allowlist exists to refuse.

probe-validation.sh now pins that: 20 refusals, including the external hostname, the
cluster-local name over https, and the cluster-local name on the wrong port.

Also corrects a remark in the handoff entry: I cited cluster-vars' GATEWAY_VIP
(192.168.1.53) as suspicious next to the nodes' 192.168.2.x. That was noise — those base
cluster-vars values are dev-era leftovers for a decommissioned cluster and say nothing
about prod. None of the measured facts depended on it.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>

infra/agent/pm-worker

@@ -90,9 +90,19 @@ esac
 # pointing at an external host would be REACHABLE: it could clone a repository that is not
 # this one and push this repository's work somewhere else. The allowlist is baked in here,
 # where changing it requires rebuilding the image whose digest admission pins.
+#
+# ONE ENTRY, AND IT IS THE CLUSTER-LOCAL SERVICE NAME. This agent runs INSIDE the cluster, so
+# it reaches Gitea the way every other in-cluster consumer does — `*.svc.cluster.local` —
+# which is by design a different path from how a client outside the cluster reaches the same
+# service. The external hostname `gitea.home.keithjackson.dev` used to be a second accepted
+# value here; it is removed deliberately. It was never needed (nothing sets it), it routes
+# in-cluster traffic out through the Gateway and back for no reason, and as an ACCEPTED value
+# it widened this allowlist to a host reachable over the `world:443` egress rule — which is
+# the exact shape of injection the allowlist exists to refuse. The cluster-local name also
+# depends on none of public DNS, Cloudflare, the Gateway or the certificate.
 case "${PM_GITEA_URL}" in
-  http://gitea.gitea.svc.cluster.local:3000|https://gitea.home.keithjackson.dev) ;;
-  *) die "PM_GITEA_URL '${PM_GITEA_URL}' is not an allowed git host (see this script's header)" ;;
+  http://gitea.gitea.svc.cluster.local:3000) ;;
+  *) die "PM_GITEA_URL '${PM_GITEA_URL}' is not the allowed in-cluster git host (see this script's header)" ;;
 esac
 [[ "${PM_GITEA_OWNER}" =~ ^[A-Za-z0-9][A-Za-z0-9._-]{0,38}$ ]] || die "PM_GITEA_OWNER is malformed"
 [[ "${PM_GITEA_REPO}"  =~ ^[A-Za-z0-9][A-Za-z0-9._-]{0,99}$ ]] || die "PM_GITEA_REPO is malformed"