Migrate to happydom

[OEvgeny]

Fixes #

Changelog Entry

(No changelog entry for internal / tests change)

Description

Replaces jest-environment-jsdom with @happy-dom/jest-environment across all test files to improve test environment stability and performance.

Specific Changes

• Updated test files across packages to use Happy DOM
• Removed jest-environment-jsdom from dependencies
• Added @happy-dom/jest-environment v15.0.0
• Fixed tests impacted by DOM implementation differences:
  • Adjusted snapshot tests for HTML output
  • Updated style attribute assertions
  • Removed XML namespace checks where not needed

-

• I have added tests and executed them locally
• I have updated CHANGELOG.md
• I have updated documentation

Review Checklist

This section is for contributors to review your work.

• Accessibility reviewed (tab order, content readability, alt text, color contrast)
• Browser and platform compatibilities reviewed
• CSS styles reviewed (minimal rules, no z-index)
• Documents reviewed (docs, samples, live demo)
• Internationalization reviewed (strings, unit formatting)
• package.json and package-lock.json reviewed
• Security reviewed (no data URIs, check for nonce leak)
• Tests reviewed (coverage, legitimacy)

[compulim]

It looks very easy to use/migrate.