Function scan

src/components/VirtualMessageList.tsx:375–383

(from: number, dir: 1 | -1, pred: (i: number) => boolean = isVisible)

    });
    const selIdx = selectedIndex ?? -1;
    const scan = (from: number, dir: 1 | -1, pred: (i: number) => boolean = isVisible) => {
      for (let i = from; i >= 0 && i < messages.length; i += dir) {
        if (pred(i)) {
          select(messages[i]!);
          return true;
        }
      }
      return false;
    };
    const isUser = (i: number) => isVisible(i) && messages[i]!.type === 'user';
    return {
      // Entry via shift+↑ = same semantic as in-cursor shift+↑ (prevUser).