feat(course): a static page and preview card for every lesson

[gHashTag]

A link to t27.ai/#/course previewed on X as the home page ("AGI game — play, direct, earn"): crawlers drop everything after #, so no lesson had a preview of its own or could be indexed.

• scripts/course-pages.mjs generates 62 static pages from course.t27: /learn/, /learn/<id>/, /ru/learn/ and /ru/learn/<id>/. Each page has:
  • the lesson's own goal, text and task;
  • canonical, reciprocal hreflang (en/ru/x-default), og + twitter summary_large_image, and JSON-LD (Course / LearningResource);
  • a link into the interactive lesson;
  • no redirect.
• A 1200x630 card per page, drawn by headless Chromium and committed. It shows the module, "Lesson n of 30", the title, the goal, the lesson widget's own card and a 30-cell progress strip. og:image carries ?v=sha12, so a new card gets a new URL.
• /learn/sitemap.xml lists all 62 pages with hreflang alternates.
• Gate: npm run check:course-pages runs in the Course CI step. It refuses a page, card (size, bytes, drawn from other words) or sitemap that lags the spec. It needs no browser: cards.json records what each card was drawn from.
• New UI strings SAY_OPEN_LESSON and SAY_OPEN_COURSE go into the spec, plus RU.

Closes #1427

{
  "version": 1,
  "head_sha": "c1d0c9bcad4dd6fe198cc3007f687c5332d62f47",
  "summary": "Every course lesson now has a static page at /learn/<id>/ and /ru/learn/<id>/ with its own 1200x630 preview card, canonical, hreflang, JSON-LD and a sitemap, so a shared link previews as the lesson instead of the home page.",
  "changes": [
    "scripts/course-pages.mjs: generates 62 pages, 62 cards rendered by headless Chromium, public/learn/cards.json and public/learn/sitemap.xml from course.generated.ts; --check verifies them without a browser.",
    "scripts/course-pages.test.mjs: one page per lesson per language, no redirect, own canonical and hreflang, card meta, the lesson words present, JSON-LD parses, sitemap lists each page once.",
    "specs/course/course.t27 and i18n/course.ru.json: SAY_OPEN_LESSON and SAY_OPEN_COURSE; generated files rewritten by course-from-spec.",
    "package.json and website-checks.yml: gen:course-pages and check:course-pages, run in the Course step."
  ],
  "tests": [
    {"command": "node scripts/course-pages.mjs --check", "result": "up to date 62 pages (en, ru), 62 cards, learn/sitemap.xml", "status": "passed", "evidence": "Local run on this branch."},
    {"command": "node --test scripts/course-pages.test.mjs", "result": "5 pass, 0 fail", "status": "passed", "evidence": "Local run on this branch."},
    {"command": "node scripts/course-from-spec.mjs --check", "result": "30 lessons in 10 modules, 45 widgets; spec tests 6, asserts 24, all hold", "status": "passed", "evidence": "Local run on this branch."},
    {"command": "headless screenshot of /ru/learn/bits-and-trits/ and of the EN and RU cards", "result": "page and cards render; long RU titles and the longest URL fit", "status": "passed", "evidence": "Screenshots read locally."}
  ],
  "limitations": [
    "X caches a card per URL: a post that already links t27.ai/#/course keeps its old card; new posts should link t27.ai/learn/ or t27.ai/learn/<id>/.",
    "robots.txt on the apex does not list learn/sitemap.xml yet; that is a separate change in the apex repo."
  ],
  "tags": ["Course", "Website", "SEO"],
  "blog": {
    "title": "Every t27 lesson now has its own preview card",
    "summary": "A course link on X showed the home page card because crawlers ignore the hash; each of the 30 lessons now has a static page and a card drawn from the course spec.",
    "outline": [
      "Why a hash route such as t27.ai/#/course is invisible to X, Telegram and search engines, and why a redirect page would not fix it.",
      "How one generator reads course.t27 and writes 62 pages, 62 cards and a sitemap, in English and Russian, with nothing written twice.",
      "How CI tells a stale card without a browser: the manifest records a hash of the card HTML and every picture and font it loads."
    ]
  }
}

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