manager events: Spawned/Rebuilt/Killed/Destroyed + start button

hive-c0re/src/coordinator.rs

@@ -107,6 +107,27 @@ impl Coordinator {
         self.transient.lock().unwrap().clone()
     }
 
+    /// Push a `HelperEvent` into the manager's inbox. Encoded as JSON in
+    /// `Message::body`; sender = `SYSTEM_SENDER`. The manager harness
+    /// recognises the sender and parses the body. Best-effort: a serde or
+    /// broker error is logged but does not propagate.
+    pub fn notify_manager(&self, event: &hive_sh4re::HelperEvent) {
+        let body = match serde_json::to_string(event) {
+            Ok(s) => s,
+            Err(e) => {
+                tracing::warn!(error = ?e, "failed to encode helper event");
+                return;
+            }
+        };
+        if let Err(e) = self.broker.send(&hive_sh4re::Message {
+            from: hive_sh4re::SYSTEM_SENDER.to_owned(),
+            to: hive_sh4re::MANAGER_AGENT.to_owned(),
+            body,
+        }) {
+            tracing::warn!(error = ?e, "failed to push helper event to manager");
+        }
+    }
+
     pub fn agent_dir(name: &str) -> PathBuf {
         PathBuf::from(format!("{AGENT_RUNTIME_ROOT}/{name}"))
     }