fix: account for :has(...) as part of :root

[dummdidumm]

We previously marked all :root selectors as global-like, which excempted them from further analysis. This causes problems:

• things like :not(...) are never visited and therefore never marked as used -> we gotta do that directly when coming across this
• :has(...) was never visited, too. Just marking it as used is not enough though, because we might need to scope its contents

Therefore the logic is enhanced to account for these special cases. Fixes #14118

While fixing this I cleaned up some inconsistencies in what we mark as global. This simplified code and fixed some adjacent bugs, which conindicentally also fixes #14189

Before submitting the PR, please make sure you do the following

• It's really useful if your PR references an issue where it is discussed ahead of time. In many cases, features are absent for a reason. For large changes, please create an RFC: https://github.com/sveltejs/rfcs
• Prefix your PR title with feat:, fix:, chore:, or docs:.
• This message body should clearly illustrate what problems it solves.
• Ideally, include a test that fails without this PR but passes with it.

Tests and linting

• Run the tests with pnpm test and lint the project with pnpm lint

[changeset-bot]

🦋 Changeset detected

Latest commit: 261d6f1

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

This PR includes changesets to release 1 package

Name	Type
svelte	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[github-actions]

Playground

pnpm add https://pkg.pr.new/svelte@14229

[Thiagolino8]

Still breaks with nesting + &: