refactor(#1865): consolidate agent + manager socket servers into one

The per-agent and manager sockets ran two parallel dispatchers with
duplicated lifecycle handlers (agent-side topology-gated, manager-side
ungated) plus a manager-only handler set. Collapse to one parameterized
server in socket_server.rs:

- one serve() + dispatch(req, agent, privileged, coord); start() binds
  the per-agent sockets (privileged=false), start_manager() binds the
  manager socket (privileged=true).
- each lifecycle/config handler (start/restart/kill/update/init_config/
  apply_commit) merges its dual: the topology guard (require_child /
  require_new_child) runs only on the !privileged path; init_config
  records the requester as parent only when !privileged. restart keeps
  the orthogonal, capability-gated + audited infra-container branch.
- the agent-state queries (loose-ends / reminder count + rollup) branch
  on privileged: privileged keeps any-target + the "*" hive-wide sweep
  (query_agent_state-gated), non-privileged keeps the topology/cap gate.
- the privileged-only verbs (schedules / meta-inputs / get_logs) plus
  the submit/schedule/watchdog helpers move into socket_server; they are
  reached via dispatch_privileged_only(), which rejects the whole group
  on a non-privileged socket.
- delete manager_server.rs; repoint refs; merge the test modules.

No behavior change: the topology guard still applies on every
non-privileged lifecycle call, the privileged socket still acts on any
agent, and privileged-only verbs are still rejected on agent sockets.

hive-c0re/src/main.rs

@@ -13,8 +13,8 @@ use hive_sh4re::{HostRequest, HostResponse};
 use hive_c0re::coordinator::{Coordinator, HiveEnv, ServeConfig};
 use hive_c0re::{
     agent_sockets, auto_update, bash_tasks_vacuum, broker, client, crash_watch, dashboard,
-    dashboard_events, events_vacuum, forge, knowledge, manager_server, matrix, migrate,
-    rebuild_queue, reminder_scheduler, scheduled_prompts_worker, server,
+    dashboard_events, events_vacuum, forge, knowledge, matrix, migrate, rebuild_queue,
+    reminder_scheduler, scheduled_prompts_worker, server, socket_server,
 };
 
 #[derive(Parser)]
@@ -265,7 +265,7 @@ async fn cmd_serve(
     // Copy value first for the dashboard + knowledge-webhook tasks.
     let dashboard_port = env.dashboard_port;
     let coord = Arc::new(Coordinator::open(&db, env, model_prices)?);
-    manager_server::start(coord.clone())?;
+    socket_server::start_manager(coord.clone())?;
     // Idempotent pre-flight: rewrite pre-meta-layout applied
     // repos, ensure proposed repos carry the `applied`
     // remote, bootstrap the meta repo, repoint containers at