feat(BaseTable): add column reordering feature

[kseniya57]

feat(BaseTable): add column reordering

Adds drag-and-drop column reordering for BaseTable / Table via a new opt-in ColumnReorderingProvider wrapper, built on top of @dnd-kit. The feature is fully additive — nothing changes unless you wrap your table in the provider.

What's new

• ColumnReorderingProvider — wrap <Table> / <BaseTable> to enable dragging column headers to reorder columns.
• Pinning-aware — pinned columns can be reordered too, but only within their own group (left-pinned, right-pinned, or center). A drag never crosses a pin boundary.
• Uncontrolled by default — with no onReorder, the provider updates the table itself (setColumnOrder for center columns, setColumnPinning within a pinned group). Pass onReorder to control/persist state yourself.
• Drag overlay — a floating preview of the dragged column (header + first rows) follows the pointer; customizable via renderDragOverlay / dragOverlayRowCount, or return null to disable.
• Visual feedback while dragging — the dragged column's content dims and a blue insertion line marks the drop position.
• Edge auto-scroll — dragging near the horizontal edges auto-scrolls the nearest scroll container (toggle with autoScroll).
• Per-column opt-out — enableColumnReordering: false in a column def; grouped/placeholder columns aren't draggable.
• activationDistance (default 8px) so header clicks (sorting, etc.) keep working.
• Theming via CSS variables — insertion line color/width, dragged opacity, and drag-overlay background/shadow/radius.

API

• New exports: ColumnReorderingProvider, ColumnReorderingContext, ColumnDragOverlay, and the ColumnReorderResult / provider prop types.
• New column-def flag: enableColumnReordering?: boolean.
• onReorder(result) returns { columnOrder, columnPinning, pinned, draggedColumnId, targetColumnId }.

<ColumnReorderingProvider
  table={table}
  onReorder={({columnOrder, columnPinning, pinned}) => {
    if (pinned) setColumnPinning(columnPinning);
    else setColumnOrder(columnOrder);
  }}
>
  <Table table={table} />
</ColumnReorderingProvider>

[gravity-ui-bot]

Preview is ready.