v4.28.0

Focus: sidebar top links that open pages of the site in place, and standalone pages that live outside every book.

Changes

• 🧭 Added in-place top links: links.changelog, links.roadmap, links.sponsor and each links.explore[].url accept the path of a page of the site (e.g. '/sponsors/'), which opens in the same tab, without the open-in-new icon, and stays highlighted while the page is open. URLs and static files keep opening in a new tab. docsector dev warns about a page-like path that matches no page.
• 🏝️ Documented standalone pages: an entry keyed '' with a book id no *.book.js defines and menu: { hidden: true } routes at /<id>/overview/, with its Markdown at src/pages/<id>.overview.<lang>.md, no book tab, no page tree and no previous/next — ideal for sponsoring, advertising or team pages opened from a top link.
• 👻 Documented menu.hidden for the first time, and made every navigation surface honour it: a book tab never lands on a hidden page, and the sidebar search index skips hidden pages.
• 🔎 The sidebar search is disabled on a page with no page tree to filter.
• 🎯 The menu auto-scroll centres the page-tree item when a top link points to the same page.
• 🛠️ Fixed the eager-mode Markdown key for a page keyed '' (including the docsector init scaffold).
• 🗂️ Added an exact _headers cache rule for single-segment documents (such as a standalone page's bare path), which the per-book wildcard never matched, in both the SPA and the SSR prerender.
• ⚠️ The build warns when a page takes a reserved route path (assets, assistant, home, mcp, and 404, feedback, index for a page keyed '') and when a standalone page is declared in an archived version.
• 🔒 Site paths in config links now reject backslashes (/\host), which browsers read as another host.
• 📚 Updated docs in both locales: Pages and Routing (Hidden Pages, Standalone Pages), Navigation Menu (Top Links, Footer Buttons), Previous & Next, Sponsors, Page Ad and Configuration, plus the README and the authoring agent skill.
• ✅ Validated with 709 unit tests, mutation checks, SSG and SSR fixture builds, and headless-browser checks on desktop and mobile.