The CSS picked dark styling via @media (prefers-color-scheme: dark), which
tracks the OS/browser setting rather than Colab's own light/dark toggle -- so
a dark OS + light Colab produced dark cards on a light page. Replaced with a
theme-agnostic stylesheet: inherit the page text color and use translucent
grey overlays for card/table backgrounds and borders, so output blends into
light or dark notebooks. Brightened the row/col accent colors for contrast
on both.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>