cancel_thread: new mcp tool — unify reminder + question cancel on both surfaces

hive-c0re/src/manager_server.rs

@@ -348,6 +348,16 @@ async fn dispatch(req: &ManagerRequest, coord: &Arc<Coordinator>) -> ManagerResp
             role: "manager".to_owned(),
             hyperhive_rev: crate::auto_update::current_flake_rev(&coord.hyperhive_flake),
         },
+        ManagerRequest::CancelThread { kind, id } => crate::questions::handle_cancel_thread(
+            coord,
+            MANAGER_AGENT,
+            *kind,
+            *id,
+        )
+        .map_or_else(
+            |message| ManagerResponse::Err { message },
+            |()| ManagerResponse::Ok,
+        ),
     }
 }