fix(#1118): coalesce multi-hop reparent notifications for offline agents

hive-c0re/src/coordinator.rs

@@ -616,12 +616,12 @@ impl Coordinator {
                     in_reply_to: None,
                 });
             }
-            let _ = self.broker.send(&hive_sh4re::Message {
-                from: hive_sh4re::SYSTEM_SENDER.to_owned(),
-                to: child.to_owned(),
-                body: format!("your parent changed from {old_label} to {new_label}"),
-                in_reply_to: None,
-            });
+            // Coalesce: if a prior move notification is already pending in
+            // the broker (agent was offline for multiple moves), update it
+            // in-place so the agent sees "A to C" not "A to B" then "B to C".
+            let _ = self
+                .broker
+                .send_coalescing_reparent(child, old_label, new_label);
         }
 
         // Rescan + diff-emit regardless of whether messages fired —