[wieslawsoltes]

Both Linux and macOS main CI stopped in the runtime compatibility pre-build after #427 because the new live style-rule serializer removed browser-required brace spacing and a final declaration semicolon. Chrome 153 serializes the reproduced quoted-brace/escaped-string/data-URL rule with one space inside each brace and a final semicolon.

This change canonicalizes the live CSSStyleRule.cssText wrapper accordingly for empty, flat, and nested rules and updates the existing token-boundary regression to the Chrome oracle. The same serialized text is published to native stylesheet state, so replacement and later declaration mutations retain one browser-shaped representation.

Closes #432
Parent: #239

Validation:

• Chrome 153 headless oracle: flat, empty, nested-media, and custom-property examples
• Node 24.18.1 focused stylesheet CSSOM: 8/8
• Node 24.18.1 full runtime compatibility: 26/26
• 300 insert/delete mutation gate: 15.14 ms focused run
• hosted Linux/macOS and portable/native gates pending
  \n