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/namespace.yaml

@@ -0,0 +1,9 @@
+# One namespace for the whole agent estate rather than one per agent. The agents
+# share nothing but a trust boundary — no data, no storage, no service mesh
+# policy — and splitting them would multiply the CA ConfigMap and the
+# ExternalSecret without isolating anything that matters. What isolates them is
+# their Keycloak client and the audiences it may request, not the namespace.
+apiVersion: v1
+kind: Namespace
+metadata:
+  name: agents