Goal for embedding a short marker in the usage/error table's bottom frame edge
(bottom-right @examples indicator, counterpart of the top 'Usage' title). Two
severable deliverables: frame-parity -subtitle/-subtitlealign on
textblock::class::table (must work with or without footer rows), and footer
rows with column spans independent of the body via configure_footer mirroring
the header API (the -show_footer/-ansibase_footer/-ansiborder_footer styling
knobs already exist but no footer-row methods do). arg_error's interim
'Example:' header row retires when this lands.
Assisted-by: harness=claude; primary-model=claude-fable-5; api-location=anthropic.com
Julian Noble