Polish a deck

make qa does the looking; this skill covers what to do with what it finds. The
layout controls themselves are documented in docs/authoring.md "Centering and scaling a
short slide". Don't restate them; use them.

Loop

1. make -C decks/<deck> qa (or make qa DECKS=<name> in a multi-deck directory). It
   builds every format, then writes _qa/report.txt, usage.tsv, <deck>-html.png
   and <deck>-pdf.png contact sheets, and per-slide PNGs.
2. Fix the failures (source ..., PDF ..., HTML ..., a slide-count MISMATCH)
   first. Then read both contact sheets yourself: the checks find overflow, not ugliness.
3. Work through the hint lines.
4. Rebuild and rerun until the report is clean. Then look at the sheets once more.
5. pptx is only counted. For a look, soffice --headless --convert-to pdf deck.pptx
   gives a contact sheet; the fonts will fall back to serif, so judge layout only.

Known fixes

Rules

• Ask before reversing a deck decision. If a decision is recorded in the deck's plan
  or handoff (for example, "bullet slides keep the deck's size"), ask before overturning it.
• Monospace goes on CLIs, daemons, packages, scripts, databases and branch names.
  Products (Kubernetes, Redis, Argo CD) and environment names stay plain. Diagram labels
  stay in one sans face.
  • List the names in qa-names.txt in the deck directory, one per line, and make qa
    reports each plain-text use. Section subtitles on the blue divider slides stay plain.
• Generated tables (frozen _out_*.qmd files written by a script): change the generator
  as well as the output, or the next refresh undoes the fix.
• Measure before scaling. usage.tsv's use column is the share of the slide body the
  content fills in HTML. Up to 0.65 has room for ×1.15.

Deferred: build these only if the friction repeats

• No ignore list. A deliberately dense demo slide (the sample's "Wall of Text") is
  reported on every run. If that gets noisy, add a qa-ignore.txt of slide kind pairs.

• Sample deck overflows found by the first make qa: p3 (the numbered list meets the
  frame number), p9 (a paragraph runs off the page) and the _quarto.yml slide (code plus
  column). Fix them, or ignore them once that list exists.

• The table-column rule is heuristic. It needs three lines starting at the same x, and it
  skips right-aligned number columns. It was tuned on this theme's longtable output. A
  different table style may need the threshold raised, or its own rule.

• The PDF right edge is 0.94 W for full-width pages and 0.97 W for column pages, which
  overhang the margin. A theme margin change moves both (EDGE / COLS_EDGE).

• Overlays: incremental pages map to one frame by the printed frame number. An
  unnumbered frame with overlays would miscount.

• Diagrams are invisible to the PDF text checks when they are mermaid PNGs. Only the
  HTML autofit hint and the contact sheet catch them.

• pptx overflow is not checked. PowerPoint autofit hides most of it. A LibreOffice
  render through the PDF checks would be the next step, with font fallback as the caveat.

• Not in CI, which would need a browser and TeX. A PDF-only mode (--no-html) is the
  likely first step.

• Speed: about 0.4 s a slide for the HTML pass. If decks grow, skip the screenshots or
  run in parallel.

• Theme follow-ups seen in the SAMuel pass:

  • revealjs inline code breaks at hyphens inside table cells;
  • two-line slide titles run into the title rule in HTML.

  Both belong in the engine (_extensions/engine/).