Convert website source from static HTML to Jekyll-powered Markdown

[Copilot]

Website pages were authored as raw HTML files committed directly to the repo. They should be Markdown source files that Jekyll compiles to HTML at publish time.

Changes

Jekyll setup

• website/_config.yml — enabled Jekyll (was explicitly disabled)
• website/Gemfile — adds jekyll ~> 4.3
• website/_layouts/home.html — layout for landing pages; Liquid-driven language switch (page.lang), nav, footer, and CSS
• website/_layouts/doc.html — layout for doc pages; sidebar with conditional EN/ZH labels, per-page nav links and active-state via front matter

Content: HTML → Markdown (8 files)

• website/index.md + website/zh/index.md
• website/docs/{getting-started,how-it-works,local-testing}.md
• website/zh/docs/{getting-started,how-it-works,local-testing}.md

Standard prose/headings/lists use native Markdown; styled components (step-boxes, callouts, syntax-highlighted code blocks) stay as raw HTML blocks since they rely on custom CSS classes.

All 8 original .html source files removed.

CI: .github/workflows/pages.yaml

Before: uploaded website/ directory directly to Pages.
After: runs bundle exec jekyll build first, uploads _site/ (compiled output).

- uses: ruby/setup-ruby@v1
  with:
    ruby-version: '3.3'
    bundler-cache: true
    working-directory: website

- name: Build with Jekyll
  run: bundle exec jekyll build --destination ../_site
  working-directory: website

- uses: actions/upload-pages-artifact@v4
  with:
    path: _site/

_site/ added to .gitignore.

Original prompt

So, right now, the document was created as HTML. Actually, it should be a Markdown file, and then when you build it and publish it, it converts to HTML.

Please:

1. Make the document as a Markdown file
2. Remove all the HTML files from the repository

And when you publish it to the GH Pages branch, it should be the HTML file.

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