Redesigned A/B model comparison panel

The A/B comparison panel has a redesigned layout: elevated per-model cards with accent hairlines, a streaming skeleton and typing indicator while answers arrive, latency chips, and a centered vote bar. After you vote, the winning card is highlighted and the loser dimmed; in blind mode the model names are revealed only once the vote is cast, and a result strip links to the comparison history.

The main answer no longer renders twice while the comparison panel is open. The redesign is pure CSS and honors reduced-motion preferences.

No action required.