An Arabic workbook, right to left

// ═══ Postext Cookbook · Nº 173 · An Arabic workbook, right to left ═══════════════
// https://postext.dev/en/cookbook/arabic-workbook-rtl
// Code: MIT · Text: original (CC BY 4.0) · Pictures: generated with diffusion models
// Fonts: Noto Naskh Arabic, Baloo Bhaijaan 2 (SIL OFL 1.1) · Needs postext ≥ 1.59.0
import {
  buildDocument, withLoadedFonts, renderPageToCanvas, registerResourceImage,
} from 'https://esm.sh/postext';
import { renderToPdf, decompressWoff2 } from 'https://esm.sh/postext-pdf';

const LANG = 'ar'; // @lang: the language of the frame; the workbook is Arabic in all
const RECIPE = 'arabic-workbook-rtl';

// ─── 1 · Design ─────────────────────────────────────────────────────────────
// #region palette: a garden workbook: ink, a terracotta accent, a leaf green, sand
const palette = {
  ink: '#22282e', // text
  accent: '#b9542a', // the one accent: exercise numbers, the unit tab, the word bank
  leaf: '#4f7d3a', // the second: rules and the word search's ruling
  sand: '#f8eedf', // the bank's ground, the answers box
  rule: '#c8b49b', // writing lines
  muted: '#6f655c', // folios, the name line, the colophon
  paper: '#ffffff',
};
const col = (id) => ({ hex: palette[id], model: 'hex', paletteId: id });
const colorPalette = [
  ...Object.entries(palette).map(([id, hex]) => ({ id, name: id, value: { hex, model: 'hex' } })),
  { id: 'main-color', name: 'accent (defaults)', value: { hex: palette.accent, model: 'hex' } },
];
// #endregion
// Naskh for the text, a rounded Arabic for the labels a child reads first.
const [TEXT, LABEL] = ['Noto Naskh Arabic', 'Baloo Bhaijaan 2'];

// #region answer: one exercise style read right to left, in the edition's digits
// The locale sets the direction, the binding and the digits: 'ar' writes the exercise
// numbers, the items and the key in Arabic-Indic digits (١ ٢ ٣), 'ar-MA' in European ones.
// Options take the abjad letters (أ ب ج), true/false the words صح / خطأ, both from the
// language. Nothing below names a side: the engine sets every part from the right.
const tamrin = {
  id: 'tamrin',
  number: { shape: 'disc', fontFamily: LABEL, background: col('accent') },
  instruction: { fontFamily: LABEL, bold: false, color: col('ink') },
  options: { layout: 'row' }, // أ) ب) ج) side by side, three to a row (columns=3)
  blank: { look: 'dots', color: col('muted') }, // a dotted line, as Arab workbooks print it
  match: { color: col('accent') },
  bank: { box: 'sunduq', order: 'shuffle' },
  area: { kind: 'lines', color: col('rule') },
  grid: { fontFamily: TEXT, rule: col('leaf'), uppercase: false }, // Arabic has no capitals
  answers: { color: col('leaf'), fontFamily: TEXT },