fix(webkit): animate code-block line entrance on the translate property

[gabriel-lisboa-azion]

Summary

• CodeBlock's line entrance (animateLines) and tab-swap line motion transition translate instead of transform: under Tailwind v4 -translate-x-2/translate-x-0 set the standalone translate property, so the slide never interpolated and lines only faded.
• The animateLines stagger drops from 300ms to 40ms per line.
• Spec, story argType and catalog say 40ms; a browser test guards the transition property.

How to test

1. cd packages/webkit && npx vitest run src/components/data/code-block/code-block.test.ts → 39 tests pass, including "line entrance".
2. Render <CodeBlock :animate-lines="true"> with a multi-line snippet and reload → each line slides in from the left while fading, 40ms after the previous one.
3. Switch tabs on a multi-tab CodeBlock → lines slide in from the direction of travel.
4. Enable reduced motion and reload → lines appear immediately.

Notes

• Visible behaviour change: animateLines blocks enter 7.5× faster. No API change.
• This PR and the hcl/graphql highlighting PR both touch .specs/code-block.md; whichever merges second rebases and recomputes the spec checksum.