The grid said repeat(5,1fr) against six windows, so Fallback sat alone on a
second row. The count now travels with the cards as --vv-win-n, so adding a
window widens the row instead of quietly starting another one. Grid rather than
flex keeps every card exactly the same width, and it steps 6→3→2 rather than
dropping straight to two — the middle step is the one a 15" panel lands on.