feat(dashboard): entity list UX — REF column, name cells, detail pages (CUST-WP-0030)

- ref-cell.js: REF column component — click=copy deeplink, dblclick=open
- field-help.js: field registry + fieldRow helper with help-tip decoration;
  FK fields (task_id, workstream_id, repo_id) render as async-linked cells
  with entity-title bubble-help on hover
- GET /token-events/{id} endpoint + get-by-id tests
- GET /repos/by-id/{repo_id} UUID lookup endpoint
- Landing pages: /token-events/[id], /workstreams/[id], /repos/[slug], /tasks/[id]
- token-cost.md: REF + Name columns on all three tables; parallel fetch of
  workstreams/tasks for title resolution
- reference.md: entity detail page URL scheme documented

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

state-hub/dashboard/src/reference.md

@@ -54,6 +54,28 @@ convention used in the Custodian State Hub.
 
 ---
 
+## Entity Detail Pages & REF Column
+
+Every entity table in the dashboard includes a **REF** column (leftmost) that shows
+the 1-based row number for the current view. Clicking the REF number copies a
+deep-link to the clipboard in the format `/data/<recordtype>/<id>`. Double-clicking
+opens that link in a new tab.
+
+The deep-link target is an entity detail page that renders all fields of the record
+in a key-value layout. Each field key is decorated with a `<help-tip>` that shows a
+one-sentence description of the field and a "Learn more" link to the relevant
+documentation section.
+
+Currently implemented record types:
+
+| Record type | URL pattern | Source endpoint |
+|-------------|-------------|-----------------|
+| `token-events` | `/token-events/<id>` | `GET /token-events/{id}` |
+
+Further record types (repos, workstreams, tasks) will be added in subsequent workplans.
+
+---
+
 ## Meta
 
 | Topic | What it covers |