docs: drop dead-claim narration for the retired loose-ends override

The PR retiring loose-ends' manager-only visibility replaced the false
claim with prose narrating its retirement, which still adds lines for
a removal. Delete the dead claim outright instead of documenting that
it used to be true: drop the three added sentences in
agent-hierarchy.md, and shorten socket_server/mod.rs's authority
comment to state only what's true now (tool-group membership for the
orchestration verbs) rather than adding an explanatory clause for the
removed capability check.

hive-c0re/src/socket_server/mod.rs

@@ -4,11 +4,9 @@
 //! you are `foo`; the manager socket simply serves as `ruth`. There is no
 //! privilege flag — both transports run the same [`serve`] / [`dispatch`]
 //! code, and authority derives uniformly from the caller's identity:
-//! tool-group membership for the orchestration verbs, and nothing else —
-//! the queries are all self-scoped, so no capability is consulted here at
-//! all. An agent-targeting verb may name any agent, so `ruth`
-//! reaches every agent exactly the way every other agent does, not via any
-//! hardcoded name match.
+//! tool-group membership for the orchestration verbs. An agent-targeting
+//! verb may name any agent, so `ruth` reaches every agent exactly the way
+//! every other agent does, not via any hardcoded name match.
 
 use std::path::{Path, PathBuf};
 use std::sync::Arc;