feat: the offline_access mandate

The standing authority the autonomous runs act under: an offline refresh token
issued by a new classic-models-mandate client for the user who authorised the
agent, stored in Vault, redeemed at trigger time.

The mandate client holds no domain audience. It cannot reach data; it can only
say who authorised whom. Direct access grants on it is a lab shortcut, noted as
such — mandating an agent is a decision a person takes, and a password grant
records no consent where the authorization code flow would.

Verified end to end: refresh gives sub=pm-user azp=classic-models-mandate with
the agent in the audience, the agent exchanges it to azp=itself and
aud=mcp-catalog, and the MCP call answers 200. sub stays the person who
mandated, azp says which agent acted.

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

deploy/agent-secrets.yaml

@@ -22,3 +22,9 @@ spec:
       remoteRef:
         key: keycloak/classic-models-realm
         property: KC_SECRET_CLASSIC_MODELS_AGENT_APPROVISIONNEMENT
+    # Redeems a mandate. Held by the workflow rather than by the adapter because
+    # it is the workflow that acts as the agent.
+    - secretKey: MANDATE_CLIENT_SECRET
+      remoteRef:
+        key: keycloak/classic-models-realm
+        property: KC_SECRET_MANDATE

deploy/flux-kustomization.yaml

@@ -37,6 +37,7 @@ spec:
       # The agents' Keycloak client secrets, so a workflow can exchange tokens
       # as the agent it represents. Created by agent-secrets.yaml beside this.
       EXTRA_ENV_SECRET: n8n-agent-secrets
+      EXTRA_ENV_SECRET_2: n8n-mandate-secrets
       EXTRA_CA_CONFIGMAP: sttlab-ca
       # "false" so a workflow can read $env.<AGENT>_CLIENT_SECRET. It means any
       # workflow on this instance can read any variable in the pod — acceptable

deploy/mandate-secrets.yaml

@@ -0,0 +1,25 @@
+# The standing authority the autonomous runs act under.
+#
+# A mandate is an `offline_access` refresh token, issued by the
+# classic-models-mandate client for the user who authorised the agent. It does
+# not expire, which is exactly why it is here and not in a workflow: it is
+# revoked by that user's session being revoked in Keycloak, and by nothing else.
+#
+# Two ExternalSecrets rather than one, because they answer to different owners:
+# the mandate is the agent estate's, the client secret that redeems it is the
+# realm's.
+apiVersion: external-secrets.io/v1
+kind: ExternalSecret
+metadata:
+  name: n8n-mandate-secrets
+  namespace: n8n
+spec:
+  refreshInterval: 1h
+  secretStoreRef:
+    kind: ClusterSecretStore
+    name: vault-n8n
+  target:
+    name: n8n-mandate-secrets
+  dataFrom:
+    - extract:
+        key: n8n/mandates