Frozen Lead Column

The component is self-contained: one file, no dependencies, the palette in --vibeui-datagrid-030-*. Server rendered: there is no state, everything rests on CSS. Only the first column is frozen (position:sticky, left:0) — unlike grids with two sticky edges, there is nothing to pin on the right here: what matters is the day you have scrolled to, not a totals column. The sticky cell carries a background of its own and border-collapse:separate, otherwise the scrolled days show through it and the column loses its line. The scrolling lives in a container with role=region, aria-label and tabindex=0, so it works from the keyboard. The shift code of every cell is duplicated in words in an aria-label — a coloured pill on its own is not enough. The theme comes from the surrounding color-scheme through light-dark(): by default the schedule lays no panel under itself, it sits directly on the page background and darkens along with it, and the opaque background is left only on the sticky column, in a separate --vibeui-datagrid-030-surface token.