+ Opt-in cell-flash via highlight-updates="flash". The ticker below mutates
+ random rows every 1.5s and reassigns .data. Updated cells briefly flash
+ amber and fade out. Requires rowKey (here "symbol"). Honors
+ prefers-reduced-motion. Row selection persists across updates — click a
+ row, then watch it stay selected as the data churns.
+
highlight-updates="flash" requires
+ rowKey to be set. Flash is disabled.
+
+