var(--bg-surface-variant) and var(--border-surface-variant) are not
defined in Cinny's vanilla-extract theme, so the select element renders
with a transparent/white background. Also native <option> elements ignore
most inherited CSS.
Fix: use folds color tokens (color.SurfaceVariant.*) for background,
border, and text color; add colorScheme:'dark' so the browser renders
the OS popup with dark styling; apply background+color to <option>
elements as a belt-and-suspenders fallback for browsers that honour it.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>