refactor(#2431): extract hive-priv-sock crate from hive-sh4re

Split the priv-socket wire types (PrivRequest/PrivResponse/PrivEvent and
friends) out of hive-sh4re into their own hive-priv-sock crate, mirroring
the existing hive-host-sock split. hive-priv — the root-privileged
helper — now depends on just this narrow protocol crate instead of the
much larger daemon-shared crate, shrinking its dependency surface and
making the privsep boundary easier to audit. No server/client
implementation lives here, only the wire contract; hive-c0re still
depends on hive-sh4re directly for everything else.

hive-c0re/src/server.rs

@@ -3,7 +3,7 @@ use std::sync::Arc;
 
 use anyhow::{Context, Result};
 use hive_host_sock::{HostRequest, HostResponse, LifecycleScope};
-use hive_sh4re::priv_proto::{InfraAction, InfraContainer};
+use hive_priv_sock::{InfraAction, InfraContainer};
 use tokio::io::{AsyncBufReadExt, AsyncWriteExt, BufReader};
 use tokio::net::{UnixListener, UnixStream};