Components: ship `.sf-card`

[jackgranatowski]

Type: components layer · Tier: v1.0 core

Summary

Ship .sf-card with __header / __body / __footer slots in @layer slashed.components.

Why

Layout staple; pairs with .sf-button as the first component batch (stable tokens).

Verified state (2026-06-20)

Commented stub only — 0 live rules in the built bundles. --sf-card-* token block present (commented) in optional/tokens.components.css.

Constraints

Additive, BEM-first, no build, no JS. Modifiers per docs/components.md: --bordered, --elevated, --interactive; slots __header/__body/__footer.

Acceptance criteria

• Implement .sf-card + slots + --sf-card-* tokens
• Modifiers render
• Tests (light + dark)
• Documented in docs/components.md
• MINOR bump only