Add GitHub Pages project site (Astro): readable + searchable book, blog, history

[schacon]

Summary

Adds a project website under site/, built with Astro, plus a workflow that deploys it to the gh-pages branch on every push to main.

What's on the site

• Homepage — hero with the book cover, chapter grid, third-edition callout, latest blog posts.
• The book, readable online — the full text rendered from the AsciiDoc sources at build time with Asciidoctor.js, split into one page per section (same strategy as builder/src/site.rs) with a sidebar table of contents, breadcrumbs, and prev/next navigation. Cross-references and image paths are rewritten to the new page URLs; the book source is never duplicated in the repo (generated output is git-ignored).
• Full-text search — Pagefind indexes the book and blog after each build; search UI at /search/.
• Blog in MDX — content collection at site/src/content/blog/ for updates and progress; two starter posts included.
• History of the book — timeline from Git's creation through the 2009 and 2014 editions to the third-edition work.
• Design — custom warm "book" theme with serif headings, styled Asciidoctor content (admonitions, callouts, sidebars, listings), dark-mode support, responsive layout.

Deployment

.github/workflows/deploy-site.yml builds the site on push to main (Node 22, npm ci, npm run build) and publishes site/dist/ to the gh-pages branch via peaceiris/actions-gh-pages. After merging, point Settings → Pages at the gh-pages branch; the site serves at https://progit.github.io/progit3/. Base path and canonical URL are overridable via BASE_PATH / SITE_URL.

Verification

• npm run build succeeds: 112 pages built, 109 indexed by Pagefind.
• Offline link check over dist/: 5,265 internal refs across 112 pages, 0 broken (the one flagged jam.html is escaped text inside a Perforce diff code listing, not a real link).
• Manual browser walkthrough of the built site (homepage → book TOC → reader pages with images and code listings → search for "rebase" with instant results → blog → history):

Note on the prose rule

The book text is rendered verbatim from the AsciiDoc sources — no book prose was touched. The site's own copy (homepage, history timeline, blog posts) is new website text written to fulfill this request; please review it as you would a draft, since it carries the project's voice.

  

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