feat: deploy the agent — image, manifests, and the Flux plumbing

Two-stage Dockerfile: the runtime image carries neither uv nor a build
toolchain, runs as uid 10001, drops every capability and needs no writable
filesystem (verified with --read-only and no tmpfs).

k8s/ is what runs, dev/ is the Flux plumbing that applies it, self-managing
after three manual applies — the same shape every kong-* repo settled on.

Three choices worth naming:

- One namespace for the estate. What isolates an agent is its Keycloak client
  and the audiences it may request, not a namespace boundary.
- The GitRepository uses anonymous HTTPS rather than SSH with a Vault-held
  deploy key. The repo is already anonymously readable on gitea, so a key would
  guard nothing while adding two objects to create by hand before anything
  deploys. If the repos ever go private this becomes the kong-* SSH pattern.
- The lab CA certificate is committed. It is a certificate, never a key, and
  checking it in means the deployment has no hidden prerequisite.

replicas: 1 is a constraint, not a default — conversation history lives in the
process, so a second replica would route a user's "yes" to a pod that never saw
the question.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

k8s/ca-configmap.yaml

@@ -0,0 +1,36 @@
+# The lab CA, so the agent can verify keycloak.sttlab.local and every gateway
+# rather than disabling verification. A CA certificate is public by
+# construction — this is the certificate, never the key, and it is checked in
+# deliberately so the deployment has no hidden prerequisite.
+#
+# Issued by the sttlab-local-ca ClusterIssuer, valid until 2026-11-24. When it
+# is rotated this file must be regenerated:
+#   kubectl -n cert-manager get secret sttlab-local-ca \
+#     -o jsonpath='{.data.tls\.crt}' | base64 -d
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: sttlab-ca
+  namespace: agents
+data:
+  ca.crt: |
+    -----BEGIN CERTIFICATE-----
+    MIIDPDCCAiSgAwIBAgIUd/utDf+f0yQR3v3qTjZqx+wvTZMwDQYJKoZIhvcNAQEL
+    BQAwGTEXMBUGA1UEAwwOKi5zdHRsYWIubG9jYWwwHhcNMjUxMTI0MTUzODQ1WhcN
+    MjYxMTI0MTUzODQ1WjAZMRcwFQYDVQQDDA4qLnN0dGxhYi5sb2NhbDCCASIwDQYJ
+    KoZIhvcNAQEBBQADggEPADCCAQoCggEBALj0sryq8qXtkShT/B+/EjVJNN/TLHIn
+    QJYc6xuUH/f7q3dYdLm4iH0XnFgrSQLUo4iqd/Mczef5iWCYwT5FFa7P17/TcLVf
+    gso0j41qNLBjGxDQGQ6Z1VCxi6oan8ow98rumjVj0E0Qgs5CX/rN+gcEmZ/TZFWU
+    qudVoztpeiVqJ0dxCIq+KMutzd1BU7BXx4VRO9Y+t1idUc7oY7BPmS2qPAN7TtXP
+    j1KhH2BgLsmF5GRhYHNS578eCltcmS2sbQ3c7GwOV96lpgF9TixEvFXeN4xk43E6
+    1COUD7CRiWAZ0XI8FMlpZGeNZeV4bbV/MqVig1ybWNOz9MDKYj3eoXUCAwEAAaN8
+    MHowHQYDVR0OBBYEFDbzYWOPr4vxa+VONs7xHbcNx70YMB8GA1UdIwQYMBaAFDbz
+    YWOPr4vxa+VONs7xHbcNx70YMA8GA1UdEwEB/wQFMAMBAf8wJwYDVR0RBCAwHoIO
+    Ki5zdHRsYWIubG9jYWyCDHN0dGxhYi5sb2NhbDANBgkqhkiG9w0BAQsFAAOCAQEA
+    tU4p5/ONXm7x4YDzSeL8NdThVLguiFur0jcTxvvPUS4NFNsnQJk4OXxBgjy1YwpL
+    3i56/4mCEd9OCQF/Hl0eFwGZBzNKlMoTA08AC/lBDvPrnVjuUu0qe/b/2KOkhESa
+    x8rQNp0o8pcj0f29nu0JfRqYGkzy0Lh2qgXhPu2iC+t2PfdleRAky1tt68wogdFL
+    TvHDsJbVo/ihsPpONlSyHfxG6bb/0Mkz64PH46TTt9GvJflEKMqDwivNFUA1P5S/
+    U4Ic8Qapnxc7h2+WbRjmYrnuygC2wMBE6rL9OF3gwCr1fkgGGRr5lVRUq2X2HZV5
+    5jqViv6eurq8O61N3vWGCQ==
+    -----END CERTIFICATE-----