Translate / sync a bilingual twin

Every lesson and topic exists in both en/ and es/ at mirrored paths. This skill keeps the pair in sync. The source is usually English; reverse the directions if translating es → en.

⚠️ The es locale is Spanish from Spain (es-ES, Castilian)

All Spanish content is peninsular Spanish (Spain), not Latin-American. The site declares es-ES (see astro.config.mjs sitemap locales). Write accordingly:

• vosotros for informal plural "you"; tú informal singular. Avoid ustedes/vos register choices that read as Latin-American.
• Castilian vocabulary: ordenador (not computadora), móvil (not celular), vale (not okay), coche, zumo, etc.
• Spain spelling/usage and natural peninsular idioms. seseo-neutral spelling is fine, but lexical choices must be Spain's.
• Humor and analogies (see lesson-copy) should land for a Spain audience — adapt references, don't translate them literally.

1. Locate the pair

en: src/content/lessons/en/<topic>/<lesson>.mdx
es: src/content/lessons/es/<topic>/<lesson>.mdx   ← same topic + lesson slug

Topics mirror the same way under src/content/{topics,lessons}/<lang>/…. Slugs and folder names stay identical across locales — only the prose and label props are translated, never the URL.

2. Keep frontmatter in parity

Copy the source frontmatter, translate title / description / tagline, and change only the locale-bound topic reference:

• es lesson: topic: "es/<topic>" (en uses "en/<topic>").
• Keep order, minutes, icon, accent, draft identical to the twin.
• Keep updated in sync (bump both when content changes).

3. Translate body, preserve structure

• Same number and nesting of ## / ### headings (they drive the ToC) — translate the heading text, keep the hierarchy.
• Keep all import { … } from '@/components/react' lines unchanged.
• Translate prose, Callout titles/bodies, MCQ/Quiz questions, options, and explanations.
• Keep math, code blocks, and client:* directives byte-identical.

4. Localize component label props (critical)

Interactive islands render UI chrome in their props — pass the Spanish labels in the es file:

• MCQ: checkLabel="Comprobar", retryLabel="Reintentar"
• Quiz: questionLabel="Pregunta", ofLabel="de", scoreLabel="Tu puntuación", restartLabel="Reiniciar", nextLabel="Siguiente", backLabel="Atrás"
• MCQ pretest: pretestLabel="Antes de leer — adivina" (+ the usual MCQ labels)
• MatchConcepts / Categorize / FillBlank: checkLabel="Comprobar", retryLabel="Reintentar", explanationLabel="Explicación", and translate instructions (e.g. "Coloca cada elemento en su grupo." / "Elige la opción correcta para cada hueco y comprueba.")
• MindMap: translate title, caption, eyebrow="Visión de conjunto", outlineLabel="Esquema", and every node label in the root tree (FillBlank text blanks — the correct answer AND its distractor options — must all be translated to Spanish)

Confirm exact prop names against src/components/react/* (or DESIGN.md) before writing — props evolve.

5. Verify parity

bun run check     # 0 errors required

Check both twins exist, share slug/order/topic, and have the same heading count. Then regenerate OG cards and stage them:

bun run pre-commit   # audit:fix + check + build + og:generate
git add public/og