drop hive and agent response fields the frontend never reads

hive-c0re/src/stores/broker.rs

@@ -54,9 +54,7 @@ pub struct Delivery {
 
 /// Intra-process broker event. `recv_blocking_batch` listens on the
 /// same channel as the dashboard forwarder; the forwarder re-emits
-/// each event as a `DashboardEvent` with a freshly-stamped seq from
-/// the Coordinator. The broker itself doesn't stamp seqs — that's a
-/// wire concern, not a storage concern.
+/// each event as a `DashboardEvent`.
 #[derive(Debug, Clone, Serialize)]
 #[serde(rename_all = "snake_case", tag = "kind")]
 pub enum MessageEvent {