docs: add permissions field to requests.cddl delegation schema

Mirror the new optional permissions field of request delegations in the
CBOR schema. Enumerate the supported values ("queries" / "all") to match
the spec, consistent with how request_type and status enumerate literals.

https://claude.ai/code/session_01WBqBka57Q7xYi4btZYfPqT

Author: claude

public/references/requests.cddl

@@ -96,6 +96,7 @@ signed-delegation = {
     pubkey: bytes
     expiration: timestamp
     ? targets: [* principal]
+    ? permissions: "queries" / "all"
   }
   signature: bytes
 }