[LiamSarsfield]

Fixes BOOST-747

Proposed changes

Modern Settings now has four collapsible sections: Cornerstone pages, Page loading, Code optimization, and Images. Headers include icons and descriptions; rules separate rows. Cornerstone starts collapsed, with the other sections open. Its summary appears in the header; its description, editor, and Prerender row appear once inside.

Reuse check

Reuse @wordpress/ui CollapsibleCard and @wordpress/icons, following Cornerstone and SEO Settings.

Related product discussion/links

See the issue referenced above.

Does this pull request change what data or activity we track or use?

No.

Testing instructions

1. Enable rsm_jetpack_ui_modernization_boost and open Boost → Settings. Check section order, default states, each toggle, and the nested Cornerstone editor.
2. Repeat at 1280 and 782 pixels, including RTL, with SCRIPT_DEBUG false.
3. Disable the filter and compare the legacy dashboard.

Production build, 436 Jest tests and eight tooltip browser tests, TypeScript, ESLint, and Stylelint pass.

All changed runtime code is modern-only; no shared translation strings changed. Legacy settings DOM is identical between merge-base and head builds (31,999 characters); legacy screenshots have zero differing pixels at both widths.

View	Before	After
Modern desktop
Modern mobile
Legacy desktop
Legacy mobile

RTL: 1280, 782. Cornerstone open at 1280.

Cornerstone open: 782, RTL 1280, RTL 782.

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[jp-launch-control]

Code Coverage Summary

Coverage changed in 2 files.

File	Coverage	Δ%	Δ Uncovered
projects/plugins/boost/app/assets/src/js/features/cornerstone-pages/cornerstone-pages-card.tsx	6/6 (100.00%)	0.00%	0 💚
projects/plugins/boost/app/assets/src/js/pages/settings/settings.tsx	5/5 (100.00%)	0.00%	0 💚

Full summary · PHP report · JS report