Remove PDF gen

[SteveLLamb]

Summary

Removes the tooling-based PDF rendering pipeline. HTML is the authoritative version of
SMPTE Engineering Documents; the generated PDF was convenience-only and consistently low
quality. Anyone who needs a PDF can use their browser's Print to PDF. This implements
the direction agreed in #407.

What changed

• Dropped the PDF build pass (scripts/build.mjs): removed the makePDF() Puppeteer +
  paged.js renderer, the PDF filename assembly, and all PDF plumbing — review-link entry,
  S3 URL, review-zip file, artifact link, and the application/pdf manifest entry (~108 lines).
• Removed the client-side paged.js injection (smpte.js): the ?media=print debug path
  that pulled paged.polyfill.js from a CDN is gone.
• Doc note (doc/main.html): reworded the tbody page-break note from "when generating
  PDF" to "when printing."

Puppeteer is intentionally retained — render() still uses headless Chromium to execute
the page and emit the authoritative static HTML. It was never PDF-only.

Also on this branch:

• Formula numbering (css/smpte.css): the equation is now centered to the page with the
  number right-aligned at the margin (3-column grid).
• Boilerplate (smpte.js): replaced literal smart-punctuation codepoints (curly
  apostrophes, ©, em dashes) with straight characters / references, in line with
  ILLEGAL_CHARS_RE.

Print CSS

The print stylesheet is kept as-is — the @media print / @page rules and break-* hints
remain so browser Print to PDF still produces sensible page breaks. Running headers/footers
are now browser-native rather than paged.js-driven.

Verification

• npm test (validation suite) — passes.
• node --check passes for build.mjs and smpte.js; module imports resolve.
• No residual makePDF / pagedjs / application/pdf references.
• End-to-end build: validated in the test-document repo by pointing its tooling
  submodule at this change and running a full publish build — produces the rendered HTML
  and zips with no PDF and no Puppeteer PDF pass.
  See SMPTE/tst123-4-private#1 (test PDF gen removal, commit 3e8008f).

Issues

Closes #407

Resolved by retiring the PDF tooling:

• Closes Footer, Page 2 (PDF Only): Missing Copyright Information #222
• Closes Cited Links Linking to Different Locations in the Document (PDF Only) #223
• Closes Various Locations (PDF Only): Pagination #253
• Closes Include document status (or similar) in generated PDF filename #281
• Closes PDF Rendering of formulas is not optimal #396
• Closes Table headers repeat on long tables #260
• Closes TOC Formatting - line leaders #259
• Closes Prevent Page breaks (keep with next) #234
• Closes Allow editors to specify page breaks #107
• Closes Code Block - formatting update (square edges) #217
• Closes Font alignment when using inline code tags #404
• Closes Title Page (HTML and PDF): Year-month same size as the document number #235
• Closes Various Locations: Code Font Baselines out of Alignment with Body Text #216

Partially addressed — PDF rendering is removed, but the HTML-side issue remains open:

• Title Page: Missing SMPTE Contact Information #254 (HTML title page still missing SMPTE contact information)

[github-actions]

Review links

Clean
Redline to current draft
Redline to most recent published edition