Summary

Restructures the docs site's top navigation so each top-level entry maps to a single user intent. The change is config-only: no markdown files are moved or renamed, no URLs change.

Why

Audited the current nav and found a few issues that hurt discoverability and intuition:

1. The "Docs" dropdown is a redundant wrapper. Users had to click Docs → Guide to reach the entry-point doc; peer projects (Vite, Oxc) put Guide at the top level directly.
2. "Options & APIs" conflates two different audiences. Options are user-facing config; APIs are programmatic surfaces — and the page it linked to (/reference/) is the auto-generated typedoc dictionary, which is distinct from the narrative API guide under /apis/.
3. Built-in Plugins and the programmatic/plugin API guide were buried. Both were sub-sections inside the shared Guide sidebar (sidebarForUserGuide), invisible from the top nav. Plugin authors and integrators had to drill into Guide and scroll the sidebar to find them — a real discoverability gap given that plugins and programmatic API are core to Rolldown's value proposition.
4. In-Depth was a separate sidebar context. Navigating from /guide/ to /in-depth/ swapped the entire sidebar, even though the two are a continuous learning path.

What changed

Top navigation

The ordering follows the user journey from broad to specialized:

• Guide — narrative learning path: Getting Started → In-Depth → Glossary
• Reference — auto-generated dictionary of every option, function, interface, type
• Plugins — Rolldown's built-in plugins (product docs)
• API — programmatic usage: Bundler API, Plugin API (with sub-topics), CLI
• REPL — external link
• Resources — Team / Contribute / Roadmap

The Guide → Reference adjacency mirrors Vite and Rspack, where users learn the basics in Guide and then look up specific options in the second slot.

Sidebars

• Guide absorbs In-Depth and Glossary as collapsed sections. Reading flows from /guide/getting-started through /in-depth/* to /glossary/* without losing sidebar context.
• In-Depth ordering within the Guide sidebar: concept-style articles (Why Bundlers, Why Plugin Hook Filter, Module Types, External Modules, Directives) come first; feature deep-dives (code splitting, CJS bundling, TLA, DCE, lazy barrel, etc.) follow. The grouping is implicit through ordering, not split into separate sub-headers (avoids forcing users to identify "is this a concept or a feature?").
• API, Plugins, and Reference each get their own sidebar so the route's surrounding context matches its top-nav identity.
• The redundant Configuration Options → /reference entry inside the API sidebar is removed (Reference is now its own top-level entry).

Footer

The "Rolldown" footer column is updated to mirror the new top-nav (Guide · Reference · Plugins · API · Contribute · REPL).

What did NOT change

• No markdown files moved or renamed.
• All existing URLs (/guide/*, /in-depth/*, /glossary/*, /apis/*, /builtin-plugins/*, /reference/*) continue to resolve.
• /reference/ content (auto-generated by typedoc) is untouched.
• The Resources dropdown items (Team / Contribute / Roadmap) and their activeMatch patterns are unchanged.