fix(#2190): replace MANAGER_AGENT fallbacks with "operator" for attribution

- loose_ends.rs: NULL submitter on legacy approval rows → "operator"
- questions.rs: NULL submitter on cancel_loose_end → "operator"
- server.rs: HostRequest::RequestSpawn submitter → "operator"
- dashboard.rs: web-UI spawn submitter → "operator"
- socket_server.rs: submit_init_config with no declared parent → "operator"
- mcp.rs: drop MANAGER_AGENT exception from check_send_allowed; keep <parent> only

hive-c0re/src/dashboard.rs

@@ -1681,7 +1681,7 @@ async fn post_request_spawn(
         hive_sh4re::ApprovalKind::Spawn,
         "",
         None,
-        hive_sh4re::MANAGER_AGENT,
+        "operator",
     ) {
         Ok(id) => {
             tracing::info!(%id, %name, "operator: spawn approval queued via dashboard");