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.