feat(#792): agent restart tool — topology-checked restart of direct children

hive-c0re/src/agent_server.rs

@@ -361,6 +361,32 @@ async fn dispatch(req: &AgentRequest, agent: &str, coord: &Arc<Coordinator>) ->
                 Err(message) => AgentResponse::Err { message },
             }
         }
+        AgentRequest::Restart { name } => {
+            // Topology check: the caller must be the direct parent of the
+            // target. This is the only authorisation criterion — no
+            // capability flag needed; parenthood is sufficient privilege.
+            if !crate::topology::children_of(agent)
+                .iter()
+                .any(|c| c == name)
+            {
+                return AgentResponse::Err {
+                    message: format!(
+                        "agent `{agent}` cannot restart `{name}`: \
+                         not a direct child in the topology tree"
+                    ),
+                };
+            }
+            tracing::info!(%agent, %name, "agent: enqueue restart for child");
+            coord.rebuild_queue.enqueue(
+                crate::rebuild_queue::QueueKind::Restart,
+                name.to_owned(),
+                crate::rebuild_queue::QueueSource::Manual,
+                format!("agent `{agent}` restart tool"),
+                None,
+            );
+            coord.emit_rebuild_queue_snapshot();
+            AgentResponse::Ok
+        }
         // Manager-only variants are not valid on the agent socket.
         _ => AgentResponse::Err {
             message: "request not supported on agent socket".to_owned(),