fix(deps): complete tailwindcss v4 migration and add missing @sanity/icons dependency

[jordanl17]

What

Fixes a cluster of latent Vercel build failures in the example apps and storybook, all caused by recent dependency changes that CI never caught (CI builds --filter=!./apps/*, so only Vercel builds the apps; the turbo remote cache also masked broken package builds until a cache miss).

• Tailwind v4 migration across every tailwind3-catalog consumer (apps/next, apps/live-next, apps/page-builder-demo, packages/visual-editing):
  • PostCSS configs switched from tailwindcss: {} to @tailwindcss/postcss.
  • CSS entrypoints switched from @tailwind base/components/utilities to @import 'tailwindcss' plus a @config directive that keeps each existing tailwind.config (preserving the typography plugin and @sanity/demo theme).
  • autoprefixer dropped from the PostCSS configs/deps (v4 handles prefixing via Lightning CSS).
• Declare missing-but-imported dependencies (previously resolved only via pnpm hoisting / a stale turbo cache):
  • @sanity/icons added to apps/next, apps/page-builder-demo, and apps/studio.
  • react added to @repo/sanity-schema.

Why

Commit 4b25bc0a (#3465) bumped the tailwind3 catalog to tailwindcss@^4.3.1 but migrated none of the consumers, so a fresh Vercel build threw on the v3 PostCSS plugin syntax. Separately, several packages/apps imported @sanity/icons / react without declaring them - fine under hoisting and while the turbo cache replayed old successes, but broken on any real rebuild. These only ever surfaced on Vercel.

Testing

• pnpm --filter @sanity/visual-editing build-storybook - passes.
• pnpm --filter @repo/sanity-schema build - passes.
• apps/next and apps/page-builder-demo next build - both compile successfully; the tailwind PostCSS and @sanity/icons errors are gone.
• pnpm build --filter='!./apps/*' - all packages build.
• Vercel preview deploys on this PR (visual-editing-next, visual-editing-storybook, visual-editing-page-builder-demo, visual-editing-studio confirmed green).

Follow-up (not in this PR)

The tailwind3 catalog now pins v4, so its name is misleading - a rename to tailwind/tailwind4 would be a small, separate cleanup.

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
visual-editing-storybook	Ready	Preview, Comment	Jun 17, 2026 11:29pm
visual-editing-studio	Ready	Preview	Jun 17, 2026 11:29pm

8 Skipped Deployments

Project	Deployment	Actions	Updated (UTC)
visual-editing-astro	Ignored		Jun 17, 2026 11:29pm
visual-editing-next-with-i18n	Ignored		Jun 17, 2026 11:29pm
visual-editing-nuxt	Ignored		Jun 17, 2026 11:29pm
visual-editing-remix	Ignored		Jun 17, 2026 11:29pm
visual-editing-svelte	Ignored		Jun 17, 2026 11:29pm
live-visual-editing-next	Skipped		Jun 17, 2026 11:29pm
visual-editing-next	Skipped		Jun 17, 2026 11:29pm
visual-editing-page-builder-demo	Skipped		Jun 17, 2026 11:29pm

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[socket-security]

Review the following changes in direct dependencies. Learn more about Socket for GitHub.

Diff	Package	Supply Chain Security	Vulnerability	Quality	Maintenance	License
	npm/​@​tailwindcss/​postcss@​4.3.1

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[jordanl17]

Also note that I'm planning on adding a CI build step of these studios to hopefully catch these sorts of regressions in the future: #3480