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/Alert.tsx

@@ -1,7 +1,10 @@
 import type { ReactNode } from "react";
 import MuiAlert from "@mui/material/Alert";
 
-/** Inline contextual alert (form/section feedback) — distinct from the global toast. */
+/**
+ * Inline contextual alert (form/section feedback) — distinct from the global toast.
+ * `onClose` is simplified to take no arguments (MUI's close SyntheticEvent is omitted).
+ */
 export default function Alert({
   severity = "info",
   children,