feat(system-prompt): cache dynamic policy context

docs/persistence-catalog.md

@@ -129,7 +129,7 @@ Source: [`packages/ui/user-approval/src/index.ts:55`](../packages/ui/user-approv
 /**
  * The session's approval policy was switched — log-only, durable,
  * replayable, never in the model transcript (the model learns the policy
- * from the prompt section and the narrator's notices). The LAST such
+ * from the cache-safe runtime-context snapshot). The LAST such
  * event is the session's override ({@link effectiveApprovalPolicy}).
  * `source: 'delegation'` marks an override seeded into a child; an absent
  * source is a runtime switch.