Update Headlamp and Vault documentation; enhance RBAC configurations in Argo CD. Modify Headlamp README to clarify sessionTTL handling and ServiceAccount permissions. Add Cilium network policy instructions to Vault README. Update Argo CD values.yaml for default RBAC settings, ensuring local admin retains full access while new users start with read-only permissions. Reflect these changes in CLUSTER-BUILD.md.

talos/runbooks/rbac.md

@@ -0,0 +1,13 @@
+# Runbook: Kubernetes RBAC (noble)
+
+**Headlamp** (`clusters/noble/apps/headlamp/values.yaml`): the chart’s **ClusterRoleBinding** uses the built-in **`edit`** ClusterRole — not **`cluster-admin`**. Break-glass changes use **`kubectl`** with an admin kubeconfig.
+
+**Argo CD** (`clusters/noble/bootstrap/argocd/values.yaml`): **`policy.default: role:readonly`** — new OIDC/Git users get read-only unless you add **`g, <user-or-group>, role:admin`** (or another role) in **`configs.rbac.policy.csv`**. Local user **`admin`** stays **`role:admin`** via **`g, admin, role:admin`**.
+
+**Audits**
+
+```bash
+kubectl get clusterrolebindings -o custom-columns='NAME:.metadata.name,ROLE:.roleRef.name,SA:.subjects[?(@.kind=="ServiceAccount")].name,NS:.subjects[?(@.kind=="ServiceAccount")].namespace' | grep -E 'NAME|cluster-admin|headlamp|argocd'
+```
+
+**References:** [Headlamp chart RBAC](https://github.com/kubernetes-sigs/headlamp/tree/main/charts/headlamp), [Argo CD RBAC](https://argo-cd.readthedocs.io/en/stable/operator-manual/rbac/).