feat: add onSortChange callback to DataTable for server-side sorting

When onSortChange is provided, DataTable operates in controlled mode:
it renders sort indicators and fires the callback on header clicks,
but skips client-side sorting — the caller provides pre-sorted data.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/design-system/composites/DataTable/DataTable.tsx

@@ -24,6 +24,7 @@ export function DataTable<T extends { id: string }>({
   rowAccent,
   expandedContent,
   flush = false,
+  onSortChange,
 }: DataTableProps<T>) {
   const [sortKey, setSortKey] = useState<string | null>(null)
   const [sortDir, setSortDir] = useState<SortDir>('asc')
@@ -31,14 +32,16 @@ export function DataTable<T extends { id: string }>({
   const [pageSize, setPageSize] = useState(initialPageSize)
   const [expandedId, setExpandedId] = useState<string | null>(null)
 
+  // When onSortChange is provided (controlled mode), skip client-side sorting
   const sorted = useMemo(() => {
+    if (onSortChange) return data
     if (!sortKey) return data
     return [...data].sort((a, b) => {
       const av = (a as Record<string, unknown>)[sortKey]
       const bv = (b as Record<string, unknown>)[sortKey]
       return compareValues(av, bv, sortDir)
     })
-  }, [data, sortKey, sortDir])
+  }, [data, sortKey, sortDir, onSortChange])
 
   const totalRows = sorted.length
   const totalPages = Math.max(1, Math.ceil(totalRows / pageSize))
@@ -52,13 +55,17 @@ export function DataTable<T extends { id: string }>({
 
   function handleHeaderClick(col: Column<T>) {
     if (!sortable && !col.sortable) return
+    let newDir: SortDir
     if (sortKey === col.key) {
-      setSortDir((d) => (d === 'asc' ? 'desc' : 'asc'))
+      newDir = sortDir === 'asc' ? 'desc' : 'asc'
+      setSortDir(newDir)
     } else {
+      newDir = 'asc'
       setSortKey(col.key)
-      setSortDir('asc')
+      setSortDir(newDir)
     }
     setPage(1)
+    onSortChange?.(col.key, newDir)
   }
 
   function handleRowClick(row: T) {

src/design-system/composites/DataTable/types.ts

@@ -20,4 +20,8 @@ export interface DataTableProps<T extends { id: string }> {
   expandedContent?: (row: T) => ReactNode | null
   /** Strip border, radius, and shadow so the table sits flush inside a parent container. */
   flush?: boolean
+  /** Controlled sort: called when the user clicks a sortable column header.
+   *  When provided, the component skips client-side sorting — the caller is
+   *  responsible for providing `data` in the desired order. */
+  onSortChange?: (key: string, dir: 'asc' | 'desc') => void
 }