Elements using bare text-gray-300/400/500/600 (proactive log ids and
timestamps, expand markers, event codes, ...) kept the light-theme gray
values in dark mode, which made them hard to read on slate-800/900.
- dark .text-gray-*:not([class*='dark:text-']) rules map them to the same
level as the other dark muted text (slate-300 #cbd5e1, slate-200/100 for
gray-700/800)
- dark:text-gray-400/600 and dark:text-slate-500 normalized to #cbd5e1
- dark:border-slate-600/700/800 (+ /50) brightened one step
- light theme unchanged
- the whole contrast block moved to src/contrast.css, appended by the
npm build scripts after Tailwind so it stays reproducible; SW cache
v95 -> v96