Build/Test Tools: Expand visual regression test coverage for admin pages.

[josephfusco]

Summary

Expands the existing visual regression test suite to cover 32 admin screens ahead of the WordPress 7.0 admin reskin. The tests capture full-page screenshots against baseline snapshots from trunk, making it easy to spot unintended visual changes as reskin CSS lands.

What changed:

• Coverage grew from a handful of pages to 32
• Dynamic content that causes false positives (dates, gravatars, admin notices, version strings) is now hidden via a shared screenshot.css stylesheet, with per-page Playwright mask options for anything page-specific (e.g. auto-generated passwords on Add User, health check results on Site Health)
• npm run test:visual now runs Playwright directly instead of through a wrapper script

Pages covered

Content: All Posts, Add New Post, Edit Post, All Pages, Categories, Tags, Comments, Media Library, Add Media

Appearance: Dashboard, Themes, Widgets, Menus, Plugins

Users: All Users, Add User, Your Profile

Settings: General, Writing, Reading, Discussion, Media, Permalink, Privacy

Tools: Available Tools, Import, Export, Export Personal Data, Erase Personal Data, Site Health, Updates

Other: Login (unauthenticated)

Testing

Prerequisites: Docker running, npm ci, and npx playwright install chromium.

1. Generate baselines from trunk:

git checkout trunk
npm run build
npm run env:start
npm run env:install
npm run test:visual -- --update-snapshots

2. Compare a feature branch against those baselines:

git checkout my-feature-branch
npm run build
# Full restart required — WordPress caches the build version during
# install, so without a restart it may skip setup and leave stale state.
npm run env:stop
npm run env:start
npm run env:install
npm run test:visual

Failures produce diff images in artifacts/ and an HTML report opens automatically.

Trac ticket

https://core.trac.wordpress.org/ticket/64671

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Props joefusco.

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[github-actions]

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