say per-agent socket where the manager socket is gone

the manager socket no longer exists; ruth's socket is the per-agent one. Fixes the wire-type crate docs, hive-sh4re manager.rs header and README, and two other mentions.

docs/turn-loop/README.md

@@ -98,7 +98,7 @@ variants regardless of who sends them):
 
 A small `Surface` trait, with one zero-sized impl, factors
 `hive-agent`'s wire types (`hive_core_agent_sock::{Request, Response}` —
-one unified enum shared by the agent and manager sockets) and its turn
+one unified enum shared by every agent socket) and its turn
 loop, so the loop itself has no per-role branches. See
 `hive-agent/src/main.rs`'s module
 doc for the trait shape.