Pin the wide layout to the viewport (height:100vh + overflow:hidden on the
root), add min-height:0 to the BODY wrapper and 3-column grid so the flex
chain actually constrains, and make the OPERATIONS panel a flex column whose
PanelContent is the scroll area (header stays pinned; the Panel root's default
overflow:hidden would otherwise clip). Columns' existing overflow-y:auto now
scrolls inside their tracks. Narrow mode keeps natural body flow.