fix(auth): authenticate producer-signed decisions before authorization

Assistant: codex
Assistant-Model: gpt-6-astra
Assistant-Session: 01a140c4-354a-7823-8f0d-8f717397f786

SCOPE.md

@@ -36,6 +36,13 @@ point, not an identity provider, and not a general secrets API.
 
 ### Decision-gated planning and OpenBao metadata apply
 
+- Source now requires independently configured responder trust and a separately
+  installed Go producer-format verifier on the serving authorization path.
+  Signatures bind admitted keys to signed evaluator/mode and exact policy
+  package/version/artifact digest; unsigned responses fail closed. This requires
+  a reviewed native deployment/key admission under WP14, still outstanding.
+
+
 - Resolves a catalog lane by catalog id or `approval.decision_ref`.
 - Resolves legacy lane decisions from State Hub by id, with tracked local YAML
   mirrors retained only for non-production and explicit throwaway demos. This is