fix(#2465): render multi-agent DAG nodes as per-agent subgraph lines

renderQueueEntry flattened entry.nodes into one arrow-joined chain
regardless of which agent each node belongs to. A multi-agent DAG
(e.g. hivectl restart --graceful with several agents) runs independent
per-agent subgraphs concurrently, no cross-agent deps, so joining them
all into one sequential-looking chain misrepresented the actual DAG
shape (mara's report: 'expected one dag that forks after the start
node into the per agent sub dags').

Group nodes by n.agent (stable, first-seen order) and render one
.rqe-nodes line per agent, with a small agent-label chip when the DAG
spans more than one. Single-agent DAGs (the common case) collapse back
to exactly the prior one-line render — no visible change there.

frontend/packages/dashboard/src/builds.js

@@ -307,27 +307,52 @@ function renderQueueEntry(entry, _byId, isChild) {
   // state glyph, live step label, and build-log link. This is the
   // node-aware render that makes queue jumps / partial progress
   // visible (e.g. reconcile running while swap failed).
+  //
+  // A DAG can span multiple agents (e.g. a hive-wide restart) as
+  // independent per-agent subgraphs with no cross-agent deps — they run
+  // concurrently, not sequentially. Joining every node in array order
+  // with a single `→` chain misrepresents that as one long sequential
+  // pipeline. Group by `n.agent` (stable, first-seen order) and render
+  // each agent's subgraph on its own line instead; single-agent DAGs
+  // (the common case) collapse back to exactly the old one-line render.
   const nodes = entry.nodes || [];
   if (nodes.length) {
-    const chain = el('div', { class: 'rqe-nodes' });
+    const groups = [];
-    nodes.forEach((n, i) => {
+    const groupByAgent = new Map();
-      if (i > 0) chain.append(el('span', { class: 'rqe-node-arrow' }, ' → '));
+    for (const n of nodes) {
-      const chip = el('span', {
+      let g = groupByAgent.get(n.agent);
-        class: 'rqe-node rqe-node-' + n.state,
+      if (!g) {
-        title: n.kind + ' · ' + n.state + (n.error ? ' — ' + n.error : ''),
+        g = [];
-      },
+        groupByAgent.set(n.agent, g);
-        (QUEUE_STATE_GLYPH[n.state] || '?') + ' ' + (NODE_KIND_LABEL[n.kind] || n.kind));
+        groups.push([n.agent, g]);
-      chain.append(chip);
-      if (n.build_log_id != null) {
-        chain.append(el('a', {
-          class: 'rqe-log-link rqe-node-log',
-          href: '/builds.html?id=' + n.build_log_id + '#buildlogs',
-          target: '_blank',
-          title: 'view build log #' + n.build_log_id,
-        }, '⎙'));
       }
-    });
+      g.push(n);
-    li.append(chain);
+    }
+    const multiAgent = groups.length > 1;
+    for (const [agent, groupNodes] of groups) {
+      const chain = el('div', { class: 'rqe-nodes' });
+      if (multiAgent) {
+        chain.append(el('code', { class: 'rqe-node-agent-label' }, agent));
+      }
+      groupNodes.forEach((n, i) => {
+        if (i > 0) chain.append(el('span', { class: 'rqe-node-arrow' }, ' → '));
+        const chip = el('span', {
+          class: 'rqe-node rqe-node-' + n.state,
+          title: n.kind + ' · ' + n.state + (n.error ? ' — ' + n.error : ''),
+        },
+          (QUEUE_STATE_GLYPH[n.state] || '?') + ' ' + (NODE_KIND_LABEL[n.kind] || n.kind));
+        chain.append(chip);
+        if (n.build_log_id != null) {
+          chain.append(el('a', {
+            class: 'rqe-log-link rqe-node-log',
+            href: '/builds.html?id=' + n.build_log_id + '#buildlogs',
+            target: '_blank',
+            title: 'view build log #' + n.build_log_id,
+          }, '⎙'));
+        }
+      });
+      li.append(chain);
+    }
   }
   const running = runningNode(entry);
   if (running && running.step) {

frontend/packages/dashboard/src/system-sections.css

@@ -161,6 +161,10 @@
 .rqe-node-cancelled { opacity: 0.55; text-decoration: line-through; }
 .rqe-node-arrow { color: var(--muted); }
 .rqe-node-log { margin-left: 0.1em; text-decoration: none; }
+/* Per-agent subgraph label, shown only when a DAG's nodes span more than
+   one agent (independent concurrent subgraphs, one `.rqe-nodes` line each —
+   see renderQueueEntry in builds.js). */
+.rqe-node-agent-label { color: var(--amber); margin-right: 0.3em; }
 .rqe-step {
   flex-basis: 100%;
   margin: 0.1em 0 0 1.8em;