Adds a "Duplicate Chess (under development)" card below the friend/AI
cards, pointing at /duplicate/ — a sibling sandbox (Andrew Freiberg's
four-player variant) served as a static sub-app at chess.sethpc.xyz/duplicate/
via a separate Caddy handler. The card is a plain anchor so it survives
through any future static-fallback rewriting.
claude (blind_chess)
fef6dcf095