Accessible data table

Rendering tabular data so it stays parseable by both eye and assistive tech via explicit row/column header association (scope), captions, zebra striping, and row-hover tracking.

grounded in: Recent self-improve commits 4f7ba08 'Distinguish essay data-table row headers from column headers', 8cd8212 'Zebra-stripe essay data tables so telemetry rows track across wide col', and 5762220 'Add a