docs migration - Value and Reference Types in Swift

Source: documentation/articles/value-and-reference-types.md
Proposed disposition: Migrate
Proposed destination: language-guides/Sources/LanguageGuides.docc/value-and-reference-types.md
Reviewer: @swiftlang/language-steering-group

Checklist

• Create a GitHub issue to track this migration
• Determine disposition (suggested: Migrate) and confirm destination
• Review source for accuracy and alignment with Swift 6 (particularly the actor content)
• Translate Jekyll markdown to DocC markdown format
  • Remove YAML front matter
  • Convert any Jekyll callouts to DocC-style callouts
  • Verify all code examples compile under Swift 6 strict concurrency
  • Update actor-related content to reflect Swift 6 concurrency model if needed
• Add article to LanguageGuides.docc/Documentation.md under a "Fundamentals" or "Types" topic group
• Run swift package generate-documentation --analyze --warnings-as-errors in language-guides/
• Preview locally with swift package --disable-sandbox preview-documentation in language-guides/
• Submit PR to this repository for language steering group review
• After merge and publication: add redirect_to: in the swift.org source file's front matter
• Submit redirect PR to swift-org-website

The migration targets language-guides/Sources/LanguageGuides.docc/value-and-reference-types.md and the remaining checklist item concerns the Swift.org source file's front matter. First verify that the migration has merged and been published, then add the redirect_to entry and submit the redirect PR to swift-org-website. Done means the redirect change is submitted.