layout-style-css v2.1.0

Changed

• Updated the ecosystem demo and documentation to use ui-style-kit-css@2.1.0 visual CSS, ui-style-kit-css/interactive-surface-theme.css, interactive-surface-css@1.5.0 state core, and Layout core as the canonical import order.
• Kept layout-style-css/integrations/ui-style-kit.css available as a frozen deprecated structural bridge for legacy UI-prefixed layout aliases.
• Updated release metadata and the GitHub Pages demo to identify the 2.1.0 package line.

Tests

• Switched demo fixtures to consume the staged UI Style Kit 2.1 manifest, visual bundle, and token bridge while locking Interactive Surface to the released 1.5.0 package.