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/Select.tsx

@@ -2,12 +2,12 @@ import MuiTextField, { type TextFieldProps } from "@mui/material/TextField";
 import MenuItem from "@mui/material/MenuItem";
 
 export interface SelectOption {
-  value: string | number;
+  value: string;
   label: string;
 }
 
 type SelectProps = Omit<TextFieldProps, "onChange" | "select" | "value"> & {
-  value: string | number;
+  value: string;
   onChange: (value: string) => void;
   options?: SelectOption[];
 };