G-088 proposed: textblock table footer block + bottom-edge subtitle

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

GOALS.md

@@ -329,3 +329,7 @@ Detail: goals/G-086-light-project-layout.md
 ### G-087 [active] Thin project layouts: injected infrastructure, fauxlink layout refs, working overlay merge
 Scope: src/project_layouts/ (payload store restructure), src/decktemplates/ (layout_refs migration to fauxlink), src/modules/punk/mix/commandset/project-999999.0a1.0.tm (project.new generation path), src/modules/punk/mix/commandset/layout-999999.0a1.0.tm, src/modules/punk/cap/handlers/templates-999999.0a1.0.tm (ref resolution), src/modules/punk/mix/#modpod-templates-999999.0a1.0/ (module-shipped refs/layouts), src/make.tcl (layout sync steps)
 Detail: goals/G-087-thin-project-layouts.md
+
+### G-088 [proposed] textblock table footer block + bottom-edge subtitle (arg_error examples marker)
+Scope: src/modules/textblock-999999.0a1.0.tm (class::table options and bottom border assembly), src/modules/punk/args-999999.0a1.0.tm (arg_error usage-table examples marker), src/tests/modules/punk/args/testsuites/args/examples.test + textblock table coverage
+Detail: goals/G-088-textblock-table-footer-subtitle.md

goals/G-088-textblock-table-footer-subtitle.md

@@ -0,0 +1,49 @@
+# G-088 textblock table footer block + bottom-edge subtitle (arg_error examples marker)
+
+Status: proposed
+Scope: src/modules/textblock-999999.0a1.0.tm (class::table options and bottom border assembly), src/modules/punk/args-999999.0a1.0.tm (arg_error usage-table examples marker), src/tests/modules/punk/args/testsuites/args/examples.test + textblock table coverage
+Goal: The usage/error table can carry a short marker embedded in its bottom frame edge (a bottom-right examples indicator, the counterpart of the top 'Usage' title), backed by textblock::class::table gaining frame-parity -subtitle/-subtitlealign and footer row support with column spans independent of the body, as the header already has.
+Acceptance: textblock::class::table renders -subtitle with -subtitlealign left|centre|right in its bottom border whether or not footer rows are present; footer rows with independent colspans render via a configure_footer/footer_colspans API mirroring configure_header; arg_error embeds its @examples marker bottom-right through the subtitle and retires the interim 'Example:' header row - all pinned by tests.
+
+## Context
+
+When a punk::args definition carries an @examples block, the usage/error table should
+advertise it without displaying the examples text itself. As of punk::args 0.12.5 this is
+an interim 'Example:  eg <id>' header row (scheme colour CLR(check)). The desired display
+is a short marker embedded at the bottom-right of the table frame - the visual counterpart
+of the 'Usage' title embedded at the top - which the table class cannot currently render.
+
+State of the table class (textblock::class::table, defined in the punk built-shell
+environment via textblock):
+- No -subtitle/-subtitlealign options. textblock::frame already has both (subtitle
+  overtyped onto the bottombar via overtype::block with -blockalign, gx0-aware -
+  see textblock frame implementation around the opt_subtitle bottombar handling).
+- Footer exists only as latent styling knobs (-show_footer, -ansibase_footer,
+  -ansiborder_footer in opts_table_defaults); there are no footer-row methods -
+  configure_header/header_colspans have no footer counterparts.
+
+## Approach
+
+Two deliverables, deliberately severable:
+
+1. Bottom-edge subtitle (the near-term need). Add -subtitle/-subtitlealign to
+   class::table with the same semantics as textblock::frame, overtyping the table's
+   bottom border line the way frame treats its bottombar. This must work whether or not
+   footer rows exist - the examples marker embedding must not depend on deliverable 2.
+   arg_error then replaces the interim 'Example:' header row with
+   -subtitle "eg <id>" -subtitlealign right (scheme-coloured; raw id, not @cmd -name,
+   which is display text and not always invocable).
+
+2. Footer block with independent spans (the fuller feature). configure_footer +
+   footer_colspans mirroring the header API, so renderers can put row-structured content
+   below the body with its own spans. The latent -*_footer styling options become live.
+   When footer rows are present the subtitle embeds in the frame edge below them.
+
+## Notes
+
+- Origin: user direction 2026-07-17 during the @examples usage-table indication work
+  (punk::args 0.12.5). The interim header row ships in 0.12.5 and is pinned by
+  examples.test atexamples_eg_and_usage_row - that pin flips when this goal lands.
+- An alternative interim considered and rejected: post-processing the rendered table in
+  arg_error by overtyping the last border line - workable but puts frame-drawing
+  knowledge in a consumer; the table class is the right owner.