* feat(website): add landing page with interactive learning roadmap
The site home was the rendered README, which neither sells the guide nor
helps learners track where they are. The new landing page explains the
value vs the official docs and turns the curriculum into a checklist
roadmap (10 modules, 60 lessons) with progress saved in localStorage.
- README now renders to guide.html; landing is index.html (English only,
since translated anchors differ)
- roadmap.json is validated at build time: every lesson heading must
resolve to an anchor, so doc drift fails the build
- light/dark theme toggle shared with the docs pages
- vendor Fraunces + Manrope; font CSS cache keyed on the request URL
- pin build_website.py PEP 723 deps to requirements.txt: markdown 3.11
mis-parses `</dev/tty>` in a code span and silently truncated the
rendered hooks page
* fix(website): address landing page review findings
