Make clickable data-table rows keyboard accessible

[forthfate]

Summary

The shared DataTable component makes rows clickable when an onRowClick handler is supplied. Those rows are mouse-accessible, but they cannot currently receive keyboard focus or be opened with the keyboard.

The component is used by the evaluation-build and evaluation-run screens, so a focused fix improves both locations.

Scope

• Make only interactive data-table rows keyboard focusable.
• Support Enter and Space to invoke the same callback as a row click.
• Preserve the current behavior that clicks on nested buttons and form controls do not trigger the row action.
• Keep non-interactive rows unchanged.

Acceptance criteria

• A keyboard user can tab to an interactive row.
• Pressing Enter or Space opens/activates the same row action as a mouse click.
• Nested buttons, inputs, selects, and textareas remain independently usable.
• The frontend build and lint checks pass.

Helpful files

• frontend/src/components/ui/data-table.tsx
• frontend/src/features/evaluation-builds/page.tsx
• frontend/src/features/evaluations/page.tsx

Please keep this focused on keyboard interaction; a broader table-component rewrite is out of scope.