Docs site: convert docs/ to MyST with GitHub Actions deployment to Pages

[mmcky]

The docs directory has grown into a real documentation set — using-skills.md, developing-skills.md, the hands-on evaluation tutorial, plus the design-review and validation records under reviews/ — and it is currently readable only as GitHub blob pages. Converting to MyST with a GitHub Actions deployment gives us a navigable site with QuantEcon-standard tooling, proper cross-references, and math rendering when the framework/tutorial content needs it.

Scope

• MyST site config (myst.yml) with an explicit TOC: the three docs/ guides, the benchmark user guide, and the evaluation framework. Content stays where it lives — the plugin's files (benchmark/README.md, benchmark/references/EVALUATION_FRAMEWORK.md) are included by the site build, never moved out of the plugin, preserving the self-contained-plugin convention in developing-skills.md.
• Source compatibility: files remain GitHub-renderable MyST-flavored markdown — the repo view and the site render from the same sources, no forked copies (per the "one canonical location" convention).
• Link integrity: relative links currently target GitHub blob paths in some places (e.g. the tutorial links ../reviews/..., benchmark README links a blob/main URL). The conversion should normalize these so they resolve in both contexts, and add a link-check to CI.
• GitHub Actions deployment: build the MyST site and publish to GitHub Pages on push to main; PRs get a build + link-check job (no deploy). Follows the same pattern QuantEcon lecture repos use.
• README points at the published site as the primary entry, with the in-repo files as source.

Non-goals

• No content rewrites — this is rendering/deployment only.
• The plugin payload must remain installable and self-contained exactly as today; the site is a view over the repo, not a restructuring of it.

Acceptance

• Site live at quantecon.github.io/skills with the TOC above; all internal links resolve; CI green on PRs (build + link check); deploy on merge to main only.

Not blocking #5 — this builds on the docs that PR lands.

[mmcky]

Delivered in #13, live at https://quantecon.github.io/skills/.

Built with mystmd, deployed by .github/workflows/docs.yml — build + offline link check on every PR, deploy only from main. The first deploy ran on the merge commit and all three jobs passed; every page resolves and BASE_URL=/skills correctly rewrites the asset and nav URLs for the project subpath.

Scope came out slightly wider than this issue described, because the audit plugin landed in the meantime: the TOC covers the three docs/ guides, both plugin guides with their reference material, and the catalog. Content stayed where it lives — myst.yml points at benchmark/README.md and audit/references/*.md in place, so there are no copies to drift and each plugin still ships its own documentation.

The link check earned its place immediately: seven links in the 2026-07-21 design review were written repo-root-relative from a file inside reviews/ and had never resolved on GitHub either. Fixed; all 113 relative links in the repo now resolve.

Two known limitations, both cosmetic and both documented in #13, since fixing either needs the content rewrite this issue ruled out as a non-goal. The plugin guides land at /readme and /readme-1 — mystmd derives slugs from filenames and ignores a slug: key in the TOC, and the alternative is YAML frontmatter that GitHub renders as a table above each plugin README. And four deep links into doctrine.md reach the right page without jumping to the section, because GitHub emits #3-read-only-boundary for a numbered heading where mystmd emits #id-3-read-only-boundary.

Not covered: qe has no plugin guide of its own (there is no qe/README.md), so it is represented on the site by the README and the catalog only. Writing one is a natural follow-up on #3.