Viewer: cross-node navigation from the detail pane (depends-on jump chips, parent/child links)

[EYH0602]

Background

Gap analysis vs the deployed ara-hub viewer (https://www.agenticresearch.sh/ara/AmberLJC/ara-paperbench/artifacts/speedrun/nanogpt-speedrun).

Problem

LinkKind::DependsOn edges (crates/ara-core/src/manifest.rs:340) are visible only as dashed lines in the graph. The detail pane offers no cross-node navigation at all: no depends-on list, no parent/child links, no breadcrumb. To follow a dependency the user must find the edge in the map and click the target node manually.

The hub renders clickable dependency chips in the detail pane that jump-select the target node and flash a .deptarget highlight on it in the map.

Proposal

• Resolve the selected node's DependsOn links (both directions: "depends on" / "depended on by") into id + label chips in the detail pane.
• Clicking a chip sets the selection to that node and briefly highlights it in the map (graph and tree modes).
• Optionally: a minimal parent ‹ N03 breadcrumb line in the detail header.

Acceptance

• Depends-on chips render in the detail pane when links exist; block omitted when empty
• Clicking a chip selects the target node in both display modes
• Target node gets a temporary highlight in the map
• Unit tests in detail.rs / scene-level tests

[EYH0602]

Fixed in #65.