topology: operator-driven move-agent via set_parent (#486)

hive-c0re/src/dashboard.rs

@@ -72,6 +72,7 @@ pub async fn serve(port: u16, coord: Arc<Coordinator>) -> Result<()> {
         .route("/cancel-reminder/{id}", post(post_cancel_reminder))
         .route("/retry-reminder/{id}", post(post_retry_reminder))
         .route("/request-spawn", post(post_request_spawn))
+        .route("/api/topology/set-parent", post(post_set_parent))
         .route("/op-send", post(post_op_send))
         .route("/meta-update", post(post_meta_update))
         .route("/api/schedules", get(api_schedules).post(post_schedule_new))
@@ -849,6 +850,17 @@ struct RequestSpawnForm {
     name: String,
 }
 
+/// `POST /api/topology/set-parent` body. `child` is required.
+/// `new_parent` may be:
+/// - omitted entirely (form field absent) → no-op error,
+/// - empty string → promote to root,
+/// - non-empty → new parent's logical name.
+#[derive(Deserialize)]
+struct SetParentForm {
+    child: String,
+    new_parent: Option<String>,
+}
+
 #[derive(Deserialize)]
 struct AnswerForm {
     answer: String,
@@ -1846,6 +1858,45 @@ async fn post_request_spawn(
     }
 }
 
+/// `POST /api/topology/set-parent` — operator-driven parent move
+/// (#486). Form fields: `child` (required, agent name), `new_parent`
+/// (optional — empty / absent string ⇒ promote to root). Refuses
+/// cycles, unknown agents, and reparenting the manager. On success
+/// re-emits container snapshots so the dashboard tree repaints
+/// without a refresh.
+async fn post_set_parent(
+    State(state): State<AppState>,
+    Form(form): Form<SetParentForm>,
+) -> Response {
+    let child = form.child.trim().to_owned();
+    if child.is_empty() {
+        return error_response("set-parent: `child` required");
+    }
+    // Empty / whitespace-only `new_parent` ⇒ promote to root. Web
+    // forms submit the empty string for a "no value" radio button,
+    // so this is the ergonomic encoding.
+    let new_parent = form
+        .new_parent
+        .as_deref()
+        .map(str::trim)
+        .filter(|s| !s.is_empty())
+        .map(str::to_owned);
+    match crate::topology::set_parent(&child, new_parent.as_deref()) {
+        Ok(()) => {
+            tracing::info!(
+                child = %child,
+                new_parent = ?new_parent,
+                "operator: set-parent via dashboard"
+            );
+            // Topology drives ContainerView.parent; refresh the
+            // snapshot so connected viewers see the new tree.
+            state.coord.rescan_containers_and_emit().await;
+            (StatusCode::OK, "ok").into_response()
+        }
+        Err(e) => error_response(&format!("set-parent {child} failed: {e}")),
+    }
+}
+
 async fn post_rebuild(State(state): State<AppState>, AxumPath(name): AxumPath<String>) -> Response {
     let logical = strip_container_prefix(&name);
     state.coord.rebuild_queue.enqueue(