builds: drop per-entry agent grouping from DAG renderer

Removes entryAgents() and the two places it rendered agent names:
- rqe-agent code element in the entry header
- rqe-node-agent-label prefix per component chain when multi-component

The DAG structure split (WCC + fan-out) already communicates subgraph
boundaries visually via the separate .rqe-nodes rows; the agent-name
labels on top of that caused layout breakage (#2666) and duplicate
information. Closes #2666.

The live build log header still labels liveNode.agent (a single specific
node, not the whole DAG) — that .rqe-agent rule is kept.

Also removes the now-unused .rqe-node-agent-label CSS rule and its
comment.

frontend/packages/dashboard/src/builds.js

@@ -157,17 +157,6 @@ function firstFailedNode(entry) {
   return (entry.nodes || []).find((n) => n.state === 'failed') || null;
 }
 
-// Distinct agents across a DAG's nodes, comma-joined for display. Agent is
-// per-node now (a DAG can span agents, e.g. a hive-wide restart), so there's
-// no DAG-level `agent` field — derive it from the nodes.
-function entryAgents(entry) {
-  const seen = [];
-  for (const n of entry.nodes || []) {
-    if (n.agent && !seen.includes(n.agent)) seen.push(n.agent);
-  }
-  return seen.join(',');
-}
-
 // Further split one weakly-connected component's topo-ordered nodes on
 // *fan-out* points — a node with more than one direct dependent — so a
 // shared gate/lock node (e.g. MetaLock, which every agent's rebuild
@@ -302,7 +291,6 @@ function rebuildQueueEntryFingerprint(entry) {
   const nodes = entry.nodes || [];
   return JSON.stringify({
     state: rollupState(nodes),
-    agent: entryAgents(entry),
     source: entry.source,
     started_at: isoToSecs(entry.started_at),
     created_at: entry.created_at,
@@ -378,8 +366,6 @@ function renderQueueEntry(entry) {
     el('span', { class: 'rqe-state', title: state }, QUEUE_STATE_GLYPH[state] || '?'),
     ' ',
     el('span', { class: 'rqe-kind' }, entry.source),
-    ' ',
-    el('code', { class: 'rqe-agent' }, entryAgents(entry)),
   );
   li.append(' ', el('span', { class: 'rqe-source rqe-source-' + entry.source }, entry.source));
   if (state === 'queued') {
@@ -411,16 +397,8 @@ function renderQueueEntry(entry) {
   // live nodes appear here; `Failed` DAGs linger until the history cap.
   if (nodes.length) {
     const components = nodeComponents(nodes);
-    const multi = components.length > 1;
     for (const compNodes of components) {
       const chain = el('div', { class: 'rqe-nodes' });
-      if (multi) {
-        const agents = [];
-        for (const n of compNodes) {
-          if (n.agent && !agents.includes(n.agent)) agents.push(n.agent);
-        }
-        chain.append(el('code', { class: 'rqe-node-agent-label' }, agents.join(',')));
-      }
       compNodes.forEach((n, i) => {
         if (i > 0) chain.append(el('span', { class: 'rqe-node-arrow' }, ' → '));
         const chip = el('span', {
@@ -456,14 +434,14 @@ function renderQueueEntry(entry) {
       class: 'inline rqe-cancel',
       'data-async': '',
       'data-confirm':
-        `cancel ${entry.source} for \`${entryAgents(entry)}\` (queue id ${entry.id})? ` +
+        `cancel ${entry.source} (queue id ${entry.id})? ` +
         `the row drops from the queue and never runs. running / done / failed entries can't be cancelled this way.`,
     });
     cancelForm.append(el('button', {
       type: 'submit',
       class: 'rqe-cancel-btn',
       title: 'cancel this queued ' + entry.source,
-      'aria-label': 'cancel queued ' + entry.source + ' for ' + entryAgents(entry),
+      'aria-label': 'cancel queued ' + entry.source,
     }, '✗'));
     li.append(cancelForm);
   }

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

@@ -159,10 +159,7 @@
 .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;