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

hive-c0re/src/job_queue/exec.rs

@@ -94,6 +94,9 @@ pub(super) async fn run_node(coord: &Arc<Coordinator>, claim: &Claim) -> Result<
         NodeKind::WriteDropin => run_write_dropin(coord, claim).await,
         NodeKind::WritePermFile => run_write_perm_file(coord, claim, &ctx).await,
         NodeKind::ApprovalDeploy => run_approval_deploy(coord, claim).await,
+        // A pure grouping anchor (boot root): no work, completes immediately so
+        // its child DAGs settle it and the boot tree resolves.
+        NodeKind::Noop => Ok(NodeOutput::default()),
     }
 }
 

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",
         }
     }
 

hive-c0re/src/job_queue/templates.rs

@@ -281,6 +281,30 @@ pub fn meta_update(
 /// Boot-time sweep parent: bump meta's hyperhive input (non-fatal),
 /// then fan out `Rebuild` children for the precomputed stale agent
 /// list (topology-sorted by the caller).
+/// Boot-time root anchor DAG: a single [`NodeKind::Noop`] node that groups
+/// this boot's `StartupSweep` + per-agent `Reconcile` child DAGs (linked via
+/// `parent_id`) into one tree so the dashboard renders the boot as one entry.
+/// Holds no lease and does no work — the children it anchors still run
+/// concurrently. `auto_update::run` submits it first (when there's any boot
+/// work), then parents the sweep + reconciles onto its id.
+pub fn boot_root(reason: String) -> DagSpec {
+    DagSpec {
+        template: Template::Boot,
+        agent: "hyperhive".to_owned(),
+        source: Source::AutoUpdate,
+        reason,
+        parent_id: None,
+        approval_id: None,
+        inputs: Vec::new(),
+        perm_payload: None,
+        transient: None,
+        nodes: vec![NodeSpec {
+            kind: NodeKind::Noop,
+            deps: Vec::new(),
+        }],
+    }
+}
+
 pub fn startup_sweep(reason: String, stale_agents: Vec<String>) -> DagSpec {
     DagSpec {
         template: Template::StartupSweep,