Course page: read the mastery law and link the X handles (blocked: foreign TSX) #1805

Boundary

• apps/website/src/pages/Course.tsx and the course generator apps/website/scripts/course-from-spec.mjs.
• BLOCKED: both are hand-written TypeScript/JavaScript. The only-t27 rule forbids adding or changing hand-written non-t27 code without the owner's owner-approved-foreign label. Nothing here starts until the owner labels it, or until t27c can generate this page from a spec.

User Scenarios

• A reader marks a lesson done by pressing "Mark as done"; the mark checks nothing. The law that replaces it exists: gHashTag/t27 specs/course/mastery.t27 (predict, poke, explain, transfer, prove; reviews after 1/3/9/27 days).
• A reader sees "On X: x.com/t27_dev and x.com/t27_lang" on the course landing as plain text; it should be two links.

Requirements

• The page reads the mastery law (through a generated module, not a hand copy of it): a prediction input before the widget, a proof input with the lesson's answer key, and progress that counts only MASTERED.
• Each course spec gains an answer key per lesson (a constant read from the lesson's spec frame), checked by the generator.
• SAY_LEAD's two handles render as links (https://x.com/t27_dev, https://x.com/t27_lang).

Success Criteria

• Pressing a button alone never fills a cell of the 27-cell grid.
• The two handles are links with rel="noopener noreferrer".

Refs #1703.