Fix site CSS/image 404s on progit3.com (base path + CNAME)

[schacon]

Problem

https://progit3.com loads with no CSS, images, or working internal links. The HTML references every asset and page under /progit3/ (e.g. /progit3/_astro/Base.BrTWN6g_.css, /progit3/book-cover.png, /progit3/book/), which 404s — GitHub Pages serves the custom domain at the root, and the files actually live at /_astro/..., /book-cover.png, etc.

The site was built with the defaults for the old project-page URL (https://progit.github.io/progit3/), before the progit3.com custom domain was attached.

Fix

• site/astro.config.mjs: default site is now https://progit3.com, default base is /. Forks can still override via SITE_URL / BASE_PATH.
• site/scripts/build-book.mjs: same default base change for the generated book pages' image paths.
• .github/workflows/deploy-site.yml: add cname: progit3.com to the publish step. The workflow uses force_orphan: true, so without this the next deploy would delete the CNAME file that currently exists on gh-pages and detach the custom domain.
• site/README.md: update the deployment URLs to match.

Verification

Built the site locally (npm run build) and served dist/ with astro preview:

• No href="/progit3 / src="/progit3 references remain anywhere in dist/.
• /, /book/, /_astro/Base.BrTWN6g_.css, /book-cover.png, /images/centralized_workflow.png, /pagefind/pagefind-ui.js, and /search/ all return 200.
• Browser walkthrough of the built site showing styles, cover image, book figures, and search all working:

Once merged, the deploy workflow republishes gh-pages and progit3.com picks up the corrected paths.

  

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