Dashboard cross-tab (pivot with >=2 dimensions) did not get #5827 row hover, and its sort story is unsettled #5836

Noticed while implementing #5827 (PR #5834), which was scoped to the FLAT dataset table only. Filed as an observation, not a defect report — nobody has asked for it.

packages/plugin-dashboard/src/DatasetWidget.tsx has two table renderers inside if (isTable):

• the flat grouped table (type: 'table', or a pivot with one dimension) — Dashboard table widget: right-align numeric columns, sortable headers, null bucket last, row hover — it currently reads as a raw dump #5827 gave it right-aligned numeric columns, sortable headers, blank-bucket-last ordering, and row hover;
• the cross-tab (type: 'pivot' with >=2 dimensions, data-testid="dataset-matrix") — untouched by that card.

The cross-tab already right-aligns its measure cells, so the worst of #5827 does not apply. What it still lacks, measured by reading the branch:

1. No row hover. Its <tr> carries only border-t; hover exists on individual drillable cells (hover:bg-accent/40 on dataset-drill-cell), never on the row. On a wide cross-tab, tracking a row across bucket columns is exactly where a row highlight earns its place.
2. tabular-nums on the row-header cells. <td className="px-2 py-1 whitespace-nowrap font-medium"> for row-dimension labels — actually these do NOT carry it, unlike the flat table's cells; noting it here only so a future sweep does not "fix" it by adding one.
3. No sortable headers. A cross-tab's axes are structural (row buckets down, column buckets across), so "click a header to sort" is not the same feature it is on a flat table — sorting rows by one across-bucket's measure is a real feature, but it is a design question, not a port of Dashboard table widget: right-align numeric columns, sortable headers, null bucket last, row hover — it currently reads as a raw dump #5827's implementation.

Item 3 is the one that needs a ruling before any code: whether a cross-tab should sort its row axis by a chosen cell column at all. Items 1 is mechanical.

Not blocking anything. Filed unassigned.