CSS theme override generation for LiveStyle.

This module handles generating theme class override rules from the manifest. Theme classes allow overriding CSS variable values when the theme class is applied.

Output Format

Theme rules use high-specificity selectors to override variable values:

.t12345,.t12345:root{--v67890:blue;}

Conditional theme values are wrapped in at-rules:

@media (prefers-color-scheme: dark){.t12345,.t12345:root{--v67890:darkblue;}}