feat(dashboard): show jobq node tree in build queue

Add NodeView::parent to the wire (hive-sh4re + hive-c0re dag_view), then
render the recursive parent/child tree in the dashboard build queue instead
of the previous flat chain/fan-out layout.

Wire change (hive-sh4re, hive-c0re):
- NodeView gains parent: Option<NodeId> (skip_serializing_if = None)
- dag_view() projects node.parent, filtering out the Dag container id
  (top-level work nodes become parent: None on the wire)

Frontend (builds.js):
- Replace nodeComponents + splitFanOut with buildNodeTree (uses parent
  edges directly) + topoSort helper (orders siblings by deps)
- renderTreeNode walks the tree depth-first, rendering indented rows
  with └─/├─ connectors and agent label per chip
- Flat chains and fan-out heuristics are gone; structure comes straight
  from the scheduler's parent axis

Closes: none (parent issue tracked in forge)

hive-c0re/src/job_queue/mod.rs

@@ -807,6 +807,15 @@ impl QueueInner {
                 Vec::new()
             };
             let has_log = self.node_rt.get(&id).and_then(|r| r.build_log_id).is_some();
+            // `node.parent` is the structural jobq parent. Top-level nodes
+            // have `parent == Some(container)` (direct children of the Dag
+            // container); those become `parent: None` on the wire since the
+            // container itself is not part of the work-node payload. Sub-nodes
+            // carry the id of their containing parent work-node.
+            let parent = node
+                .parent
+                .filter(|&p| p != container)
+                .map(hive_jobq::NodeId::get);
             nodes.push(NodeView {
                 id: id.get(),
                 agent: node.payload.agent().to_owned(),
@@ -819,6 +828,7 @@ impl QueueInner {
                 approval_id,
                 inputs,
                 has_log,
+                parent,
             });
         }
         if nodes.is_empty() {