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-sh4re/src/jobs.rs

@@ -127,6 +127,12 @@ pub struct NodeView {
     /// store-only nodes don't render a link that 404s.
     #[serde(default)]
     pub has_log: bool,
+    /// Structural parent in the jobq tree — `None` for top-level nodes
+    /// (direct children of the DAG container). Sub-nodes carry the id of
+    /// their containing parent node. The client uses this to render the
+    /// recursive tree rather than inferring structure from `deps` alone.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub parent: Option<NodeId>,
 }
 
 /// A queued / running / failed DAG — a thin projection of one container