Document deployment-managed cache permissions

docs/policy/architecture.md

@@ -293,6 +293,15 @@ an invocation that explicitly requests resume. Debug is never a cache input and
 is never created without an explicit request. Pipeline modules receive
 collaborator interfaces and never physical roots.
 
+Deployments own cache access policy. Cache writers request conventional maximum
+creation modes and let the process umask, setgid inheritance, and default ACLs
+determine effective access. Notarius owns the separate safety boundary:
+confined paths, symlink rejection, atomic publication, validation, and
+recovery. It does not chmod, chown, chgrp, or migrate cache entries to impose
+an application policy. This rule applies to chunk-plan and checkpoint cache
+only; output and debug retain their separate contracts. [Operations](../operations.md)
+owns deployment provisioning and retention guidance.
+
 Only accepted, completely validated producer output is reusable checkpoint or
 chunk-plan state. Rejected, structurally invalid, and validation-incomplete
 results cannot become cache or checkpoint inputs, even when a