fix(mui): review fixes — Select string contract, DataTable aria-sort, sx/page-clamp/dev-warn

Select value/option restricted to string (MUI sets the literal child value; string|number + onChange:string was a type lie). DataTable sortDirection uses ?? 'asc' so aria-sort is never undefined on the active column. StatusChip sx-merge drops undefined; Pagination clamps page into range; DataTable dev-warns on sortKey without onSort; Alert onClose JSDoc.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/admin/ui/StatusChip.tsx

@@ -19,7 +19,7 @@ export default function StatusChip({
       onClick={onClick}
       sx={[
         { fontWeight: 600, ...(onClick ? { cursor: "pointer" } : {}) },
-        ...(Array.isArray(sx) ? sx : [sx]),
+        ...(Array.isArray(sx) ? sx : sx ? [sx] : []),
       ]}
       {...props}
     />