A two-pane shell for docs-style reading — sticky scroll-spy nav on the left, a scrollable prose column on the right.

Scroll this column and watch the left nav highlight follow — that's an IntersectionObserver watching every registered section, not a manual scroll handler.

Each GuideSection registers its own DOM ref via theregisterRef render-prop GuideShell forwards. No section needs to know about any other section.

Lead is the opening line of a section — slightly larger.

P is the workhorse paragraph weight, muted by default.

The left sidebar takes an array of GuideNavGroup, each with a label and its own list of items. A single-group page (like this one) renders one labeled header; a longer guide can pass several groups to break a large nav into named sections instead of one long undifferentiated list.

Group labels are rendered as small uppercase kickers with a hairline rule trailing off to the right — the same visual language as the sectioneyebrow below, so the nav and the content column read as one system rather than two competing typographic voices.

Above the section nav, an optional subpages prop renders a small tab switcher between sibling guide pages — think "Guide" versus "API Reference" versus "Changelog" for the same feature. Each tab is a{ to, label, exact? } pair rendered through thelinkComponent you already pass for in-page nav links.

The active tab is derived by comparing the current pathnameagainst each tab's to: an exact match when exactis set, a prefix match otherwise, so a nested route under a subpage still highlights its parent tab.

This section's heading has an eyebrow — the small "Detail" kicker above the title, same treatment the very first section uses ("Extracted"). It's optional per-section, not a running header, so use it to flag the handful of sections that need a label — a status, a category, a difficulty — and leave the rest without one.

Overusing it flattens the signal: if every section has an eyebrow, none of them stand out, and the kicker starts reading as decoration instead of information.