The tag editor's active row barely differed from the menu background. Drive
the highlight off the roving `data-active` attribute (reliable across click-
vs key-open, unlike :focus-visible, which a click-open's programmatic focus
doesn't trip) and tint it with the accent. `bg-accent/NN` can't be used —
the theme's --accent is a hex var and Tailwind v3 can't inject alpha into it
— so use a color-mix arbitrary value, matching the app's glass idiom.