feat(#2392): group boot sweep + reconciles under one boot dag

hive-c0re/src/job_queue/model.rs

@@ -125,6 +125,12 @@ pub enum NodeKind {
     /// deploy stays inside `actions.rs` in v1 — deliberately not
     /// modeled as scheduler nodes (see the design doc §9).
     ApprovalDeploy,
+    /// No-op anchor that completes immediately with no work. It exists so a
+    /// boot's `StartupSweep` + per-agent `Reconcile` child DAGs can hang off
+    /// one root (`parent_id`) and render as a single boot tree on the
+    /// dashboard. Holds no lease and no build slot; the child DAGs it anchors
+    /// still run concurrently — the grouping is a display link, not a dep edge.
+    Noop,
 }
 
 impl NodeKind {
@@ -144,6 +150,7 @@ impl NodeKind {
             NodeKind::WriteDropin => "write_dropin",
             NodeKind::WritePermFile => "write_perm_file",
             NodeKind::ApprovalDeploy => "approval_deploy",
+            NodeKind::Noop => "noop",
         }
     }