fix(course): capstone extras as links, progress counts live lessons

[gHashTag]

Fixes from an audit of #/course after #1420.

• Empty frame in the capstone. Its extra widget wars is a site tab (preview: null), and the lesson page framed it anyway. Extras without a framable page now open as links in their own row, outside the tablist, so the tabs stay valid ARIA.
• Progress. Saved ids of lessons the course no longer has are dropped, so "N of 30" cannot run high after a rename; a finished course offers Start instead of "Continue" to lesson 1.
• Lesson 12 says "seven backends" but named six languages; it now says Verilog comes two ways (straight and through the HIR), in EN and RU.
• The website-checks comment counts 30 lessons (27 and a lab of 3).

Closes #1424

{
  "version": 1,
  "head_sha": "3c4ce84c872972b6c797674d2af6f2f4fa73a6ee",
  "summary": "The course's capstone no longer frames a widget with no page, saved progress counts only live lessons, and lesson 12 names all seven backends.",
  "changes": [
    "src/pages/Course.tsx: extras with no preview render as links in a row outside the tablist; readDone keeps only ids the course has; the overview offers Start when every lesson is done.",
    "specs/course/course.t27 and i18n/course.ru.json: lesson 12 says Verilog comes two ways, straight from the spec and through the HIR; generated files rewritten by course-from-spec.",
    ".github/workflows/website-checks.yml: the course comment counts 30 lessons."
  ],
  "tests": [
    {"command": "node scripts/course-from-spec.mjs --check", "result": "30 lessons in 10 modules, 45 widgets, 10 lesson specs compile clean; locales en, ru; spec tests 6, asserts 24, all hold", "status": "passed", "evidence": "Local run on this branch."},
    {"command": "npm run test:course", "result": "15 pass, 0 fail", "status": "passed", "evidence": "Local run on this branch."},
    {"command": "npm run typecheck:ratchet", "result": "179 errors across 26 files; baseline 179 across 26; no file gained", "status": "passed", "evidence": "Local run on this branch."},
    {"command": "vite build, then vite preview of #/course/capstone", "result": "the WARS extra shows as a link to #/queen?tab=wars; the gatle widget frames as before", "status": "passed", "evidence": "Local preview read in the browser."}
  ],
  "limitations": [
    "eslint reports react-hooks/set-state-in-effect in Course.tsx; it is on main already and this PR does not touch that effect.",
    "Ordering of the tutorial specs across lessons and per-lesson preview cards are left for a separate change."
  ],
  "tags": ["Course", "Website"],
  "blog": {
    "title": "Small fixes to the t27 course after launch",
    "summary": "An audit of the 30-lesson course found an empty frame in the capstone, a progress count that could run high and a lesson that named six of seven backends.",
    "outline": [
      "Why a widget with no framable page, such as the WARS tab on the Queen board, now becomes a link in its own row instead of an empty iframe.",
      "Counting progress only against lessons the course still has, so a renamed lesson cannot push the count past 30, and what a finished course offers.",
      "The seventh backend: Verilog written a second way, through the HIR, and why lesson 12 now names it in English and Russian."
    ]
  }
}

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