Parent

#4792

What to build

Migrate SASS tokens in bpk-component-content-cards to CSS custom properties with SASS fallbacks.

Tokens with CSS vars:

• $bpk-border-radius-md → var(--bpk-radius-md, ...)
• $bpk-text-secondary-day → var(--bpk-text-secondary, ...)

Gap — keep as bare SASS token:

• $bpk-one-pixel-rem — hairline border utility

No themeAttributes.tsx needed — no --bpk-private-content-cards-* vars exist.

Acceptance criteria

• Covered tokens replaced with var(--css-var, tokens.$sass-fallback)
• Gap token left as bare SASS token with a comment
• Storybook stories updated to include a dark mode story
• Existing tests pass unchanged
• No new CSS custom property names invented

Blocked by

None — can start immediately.