Support site section groups

[zenoachtig]

This PR restyles the site section group items and adds support for multiple section groups within a section group.

Restyle site section group items

Before

After

Improved column support

Before

After

Support nested section groups

In Tabs

Sidebar list also supported

[linear]

RND-8060 Add "headers" to site section groups

[changeset-bot]

🦋 Changeset detected

Latest commit: 7120605

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
gitbook	Patch

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[Copilot]

Pull Request Overview

This PR adds support for nested site section groups by restructuring the data model from a flat sections array to a hierarchical children structure, and updates the UI components to handle multiple levels of nesting in both tab and sidebar list views.

• Refactors site section groups to use children instead of sections for hierarchical structure
• Updates UI components to recursively render nested section groups
• Improves styling for section group tiles with better visual hierarchy

Reviewed Changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
packages/gitbook/src/lib/sites.ts	Adds recursive flattening utilities and updates site structure traversal logic
packages/gitbook/src/components/SiteSections/encodeClientSiteSections.ts	Changes data model from sections to children and adds recursive encoding
packages/gitbook/src/components/SiteSections/SiteSectionTabs.tsx	Updates tab component to handle nested groups with improved styling and layout
packages/gitbook/src/components/SiteSections/SiteSectionList.tsx	Updates sidebar list to support nested groups with proper indentation
package.json	Updates @gitbook/api dependency version
.changeset/fluffy-clouds-tap.md	Adds changeset entry for the feature

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[github-actions]

Summary of the deployments:

Version	URL	Status
Vercel	https://gitbook-v2-a7ec3q4hs-gitbook.vercel.app	✅
Cloudflare	https://4d1a7048-gitbook-open-v2-preview.gitbook.workers.dev	✅

Test content

Site	2v	2c
GitBook	https://gitbook-v2-a7ec3q4hs-gitbook.vercel.app/url/gitbook.com/docs	https://4d1a7048-gitbook-open-v2-preview.gitbook.workers.dev/url/gitbook.com/docs
E2E	https://gitbook-v2-a7ec3q4hs-gitbook.vercel.app/url/gitbook.gitbook.io/test-gitbook-open	https://4d1a7048-gitbook-open-v2-preview.gitbook.workers.dev/url/gitbook.gitbook.io/test-gitbook-open

[argos-ci]

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Build	Status	Details	Updated (UTC)
customers-v2 (Inspect)	👍 Changes approved	8 changed	Sep 18, 2025, 1:20 PM
v2-cloudflare (Inspect)	👍 Changes approved	1 changed	Sep 18, 2025, 1:24 PM
v2-vercel (Inspect)	✅ No changes detected	-	Sep 18, 2025, 1:23 PM