Implement GH-DEC-2026-003 consume-before-OpenBao PEP gate

Every live privileged production handler CAS-consumes through
approval-engine before OpenBao. Conflict, unavailability, or a missing
binding fail closed. Live production remains disabled until the durable
decision record is served.

Record kings-guard assent on the secret-use evidence contract.

Assistant: grok
Assistant-Session: 01a05f07-ae72-7781-9fcb-19efd61add00

layer.yaml

@@ -88,9 +88,11 @@ proposed_capabilities:
     owner_status: proposed
     contract: docs/secret-use-evidence-contract.md
     blocked_on: >-
-      Contract published; kings-guard has not assented. Local JSONL, the
-      load-bearing outbox, and `route`/`audit` are not this observation
-      API. Completeness is not claimed.
+      Contract published; kings-guard assented 2026-09-01 (message
+      75ebd2cc-a166-4676-94aa-deef2791c0c9) and will not treat this as an
+      observation input until the surface ships and publishes its cadence
+      declaration. Local JSONL, the load-bearing outbox, and `route`/`audit`
+      are not this observation API. Completeness is not claimed.
     review: "2026-11-28"
     consequence: >-
       kings-guard secret-abuse posture stays fixture-driven.
@@ -123,6 +125,19 @@ non_tooling_clients:
       endpoint that would serve the object is not yet available; production
       live actions therefore fail closed (see pep-stance.yaml).
 
+  - id: approval-engine-consume
+    target: approval-engine
+    layer: engine
+    modules:
+      - src/secrets_engine/approval_consume.py
+    operation: "POST /v1/approvals/{id}/consume before a production OpenBao write"
+    write: true
+    note: >-
+      PEP CAS consume under GH-DEC-2026-003. Not a decision surface. Conflict,
+      unavailability, or a missing binding fail closed; OpenBao is not
+      called. Production also remains fail-closed until a durable consume
+      binding is served.
+
   - id: key-cape-service-auth-scaffold
     target: key-cape
     layer: tooling