Shimmer marks live status text without changing its content. Its root always
carries sui-shimmer; animation and gradient styling apply only while active.
Reduced-motion environments render muted text with no animation.
active defaults to true; set it false to keep ordinary inherited text
styling.
The same chatScrollerCss block ships .sui-scroll-fade: apply it to a
scrollable element with data-fade-top="true|false" and
data-fade-bottom="true|false". MessageScroller manages those attributes
automatically.