Root cause: brand-950 was used in 13+ files but never defined in
tailwind.config.ts (brand colors only went 50-900). All dark:bg-brand-950
classes produced no CSS output, making dark backgrounds invisible.
Fix: add brand-950 mapped to --accent-900 CSS variable (same as 900,
the darkest shade available). This makes all existing brand-950 classes
work across the entire codebase.
Co-Authored-By: claude-flow <ruv@ruv.net>