Opt-in even-split fill for resizable columns. Drop <DataTableColumnAutoFit/> next to <DataTableColumnResize/> and the resizable columns grow by an equal share of the leftover space on load (the alternative to the default single-flex-column fill). Self-contained — the body ships no auto-fit code unless you install this.
pnpm dlx shadcn@latest add "https://niko-table.com/r/data-table-column-auto-fit.json"