v0.21.0

Changed

• LHS sidebar / content overlap fixed at common laptop widths (#387, #388) — at viewports 1024–1499px (most laptops: 1280, 1366, 1440), .qe-main now pushes content right via a :has(.qe-sidebar:not(.inactive)) conditional padding-left so the centered 900px content column no longer slides underneath the fixed sidebar. At viewports ≥1500px there's natural room for the sidebar as a left rail with content centered in the viewport (the established three-column look). Below 1024px the sidebar remains a drawer overlay (toggle to open). The pre-existing box-shadow: ... 9999px white halo workaround at ≤1340px is removed — it was masking the overlap; no longer needed now that the layout handles it.
• Toolbar repositioned sticky → fixed (#387, #388) — lets the LHS sidebar extend visually to the viewport top, anchoring it to the same top-left corner as the toolbar's toggle button. Content's toolbar clearance moves from .qe-main to .qe-page (no visible change to content position).
• Books built with this theme will see a small layout shift at 1024–1499px viewports on upgrade — content gets a left margin in that zone instead of overlapping the sidebar. Downstream sites should re-verify their snapshots / visual review.

Fixed

• RHS "On this page" TOC truncated on long lectures (#387) — .qe-page__toc .inner.sticky now has a bottom fade-mask hint and switches to overflow-y: auto with a discreet scrollbar on :hover / :focus-within, so overflowing TOC entries are reachable.

CI

• Split visual regression CI into build / visual / preview jobs (#394) — the Netlify preview now deploys regardless of whether visual tests pass, since reviewers need the preview link to decide whether failing visual tests reflect intentional design changes (in which case they /update-snapshots) or genuine regressions. Previously the preview was a later step of a single job and got skipped on visual-test failure. visual and preview both consume the fixtures build artifact produced by build; visual failure no longer blocks preview deploy.
• Visual regression tests migrated to the quantecon-book-theme-fixtures repo (#390, #392) — replaces the old lecture-python-programming dependency (cloned + conda-built per run, ~3–5 min) with the curated quantecon-book-theme-fixtures repo (pip-built in ~30–60s, pinned to a fixed SHA so test input doesn't drift between PRs). Adds first-ever <dl> / glossary coverage. #392 landed the update-snapshots.yml half early so the issue_comment-triggered workflow on main stayed consistent with the new fixture paths.
• Cleared all open Dependabot security alerts (#385) — npm audit fix plus major bumps of two build-time devDependencies (css-minimizer-webpack-plugin 7→8, sass) to clear serialize-javascript advisories. Transitive dev/build-time only; no runtime or shipped theme code changed.
• Bump actions/upload-pages-artifact from 4 to 5 (#382)
• Bump conda-incubator/setup-miniconda from 3 to 4 (#383)
• Bump codecov/codecov-action from 6.0.0 to 6.0.1 (#386)
• Bump actions/download-artifact from 7 to 8 (#395)
• Bump daun/playwright-report-summary from 3 to 4 (#396)