fix(node): pin gitea to the Gateway VIP — containerd was resolving it to the non-hairpinned WAN

The pm-agent image pull failed TLS verification, and the previous entry on this branch
recorded it honestly as not diagnosed. Diagnosed now, and it is not about the image.

containerd pulls as a NODE process, so it resolves through node_baseline_dns_servers (the
LAN gateway, deliberately not PiHole) and gets the public answer: a CNAME to
wan.home.keithjackson.dev -> 136.51.115.252, measured via both 1.1.1.1 and 8.8.8.8. This
router does not hairpin, so WAN:443 answers with its own placeholder certificate —
measured with the right SNI from the workstation:

    subject=C=ZZ, ST=Somewhere, L=Unknown, O=%D342e7e6b, CN=%D
    No extensions in certificate

No extensions means no subjectAltName, which is exactly 'certificate is not valid for any
names'. Meanwhile 192.168.2.20 IS the shared Gateway's VIP and its https listener serves
the real Let's Encrypt *.home.keithjackson.dev. The Gateway, the wildcard cert and the
digest were never implicated — only the node's answer.

This file already documents the identical failure for the Keycloak issuer, measured from
k3s-prod-2/-3 on 2026-10-03 (curl exit 60, ssl_verify_result=18), and already carries the
mechanism that fixes it. gitea is simply the second node process to need it; containerd is
a node process and nobody had added it. An operator must run the node_baseline play.

Also records, where an operator reads them, that the agent authenticates to Gitea with a
local account and a scoped PAT by decision — and why the federated alternative is not
merely unchosen but unavailable: Gitea implements only the Authorization Code Grant and
validates no third-party OIDC token, so a Keycloak service-account token cannot
authenticate to its API or to git-over-HTTP.

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

runbooks/pm-agent.md

@@ -68,7 +68,7 @@ Work through these in order; the first three are by far the most likely.
 |---|---|---|
 | `GET /user returned no login — is GITEA_TOKEN valid?` and a CrashLoop | the credentials are still the committed **placeholders**, or the token was revoked | fill them in per `platform/pm-agent/pm-agent-credentials.sops.yaml.example` |
 | `ImagePullBackOff`, digest `sha256:0000…` | the image has never been pushed; the committed digest is the deliberate placeholder | `infra/agent/build-image.sh`, operator pushes, then one PR updates the digest in **both** `deployment.yaml` and `configmap.yaml` (`PM_WORKER_IMAGE`) — but read the row below first |
-| `ImagePullBackOff` with `x509: certificate is not valid for any names` | the **node** cannot verify the registry's TLS certificate. Nothing to do with the digest: a correct digest fails identically. The same name serves a healthy Let's Encrypt wildcard from the LAN, so what the node reaches is not what you reach | not diagnosed — see `decisions/2026-10-05-pm-agent-registry-pull-prereq.md` for everything measured. Check the nodes' resolution of `gitea.home.keithjackson.dev` and their registry trust (`/etc/rancher/k3s/registries.yaml`), neither of which this repository declares |
+| `ImagePullBackOff` with `x509: certificate is not valid for any names` | **diagnosed.** containerd pulls as a node process, resolves through the node's public upstreams, and gets the CNAME to the WAN IP — which this router does not hairpin, so it answers :443 with its own `CN=%D` placeholder certificate (no SANs at all). Nothing to do with the digest, the Gateway or the wildcard cert | the `/etc/hosts` pin for `gitea.{{ k3s_base_domain }}` → `192.168.2.20` in `infra/ansible/inventory/group_vars/k3s_prod/vars.yml` fixes it — the same pin the Keycloak issuer already has. **Run the `node_baseline` play** for it to reach the nodes. Full evidence: `decisions/2026-10-06-pm-agent-node-resolves-gitea-to-wan.md` |
 | `ImagePullBackOff` with `401 Unauthorized` once TLS works | the pull is unauthenticated. An anonymous client gets nothing from this Gitea's registry, and no `imagePullSecret` exists anywhere in the tree | add one (a `dockerconfigjson`, SOPS-encrypted like `pm-agent-credentials`, referenced from the Deployment **and** the committed worker Job template) or allow anonymous reads of the package in Gitea — a posture decision, so yours |
 | `PM_WORKER_IMAGE must be digest-pinned` | someone put a tag in the ConfigMap | use the digest from `podman push --digestfile` |
 | `scope: ONLY issues labelled 'agent'` | `PM_REQUIRE_LABEL` is set; unlabelled issues are out of scope by configuration | label the issue, or clear the knob |