Group-by switch + reorderable lanes

Board structure, live: switch the lane axis at runtime (Status / Assignee / Priority) and the board re-buckets, and drag a lane header to reorder the columns. Both built-in - the group-by switch resets card positions to the new field; lane order is tracked and persists with persistKey. Board / Table switcher.

A live, editable Svelte 5 data grid example. Open the interactive demo or read the documentation.