fix(gateway): require admin for chat config writes

docs/gateway/protocol.md

@@ -149,6 +149,10 @@ Common scopes:
 - `operator.approvals`
 - `operator.pairing`
 
+Method scope is only the first gate. Some slash commands reached through
+`chat.send` apply stricter command-level checks on top. For example, persistent
+`/config set` and `/config unset` writes require `operator.admin`.
+
 ### Caps/commands/permissions (node)
 
 Nodes declare capability claims at connect time: