The server-warning rows composited their level tint (amber/red) over
`transparent`, so only 16-18% of the colour was opaque. Because the bar
is `position: sticky; top: 0`, page content scrolled up behind it showed
through the see-through background. Composite the tint over the elevated
surface grey (--bg-elev) instead, so the bar reads as a solid grey strip
with the level tint on top — no bleed-through. Affects every page that
shows the banner (the flow page is where it was spotted).
d14d79ce3b