Light theme has no background image, so the adaptive :root glass (94%) rendered
as flat snow-white islands, while the Plex filter rail (still on bg-surface/40)
showed the ambient tint — an inconsistency. Fix centrally, not per-component:
- index.css: one html[data-theme="light"] token override (surface 62 / card 74 /
menu 86) so every .glass* surface is translucent in light and picks up the
ambient tint, like it refracts the backdrop in dark.
- PlexSidebar: bg-surface/40 -> glass, so all filter rails bind to the same token.
One central lever now controls the light-theme glass translucency for the whole app.