hive-c0re: replace the agents_crashing banner with a crash-watcher log line + grafana alert

hive-agent/src/main.rs

@@ -118,8 +118,9 @@ async fn main() -> Result<()> {
 // ---------- shared turn helpers ----------
 
 /// Surface a `SYSTEM_SENDER` message in the live event bus + tracing
-/// log. Both agents and the manager receive `ContainerCrash`,
-/// notifications, and friends; the parse and log path is
+/// log. Both agents and the manager receive `HelperEvent` notifications
+/// (just `NeedsUpdate`, now that a container crash is a log line instead
+/// of a `ContainerCrash` event); the parse and log path is
 /// identical. Quiet no-op when `from` isn't
 /// `SYSTEM_SENDER`.
 fn log_system_event(bus: &Bus, from: &str, body: &str) {