fix(mui): ConfirmDialog retains text during close transition (no empty fade-out)

The message was bound to the caller's selected row, which gets nulled on close at the same instant the Dialog begins its fade-out — so it faded out with empty text. Now the dialog caches the last shown title/message and renders that through the exit transition.

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

src/admin/ui/ConfirmDialog.tsx

@@ -1,3 +1,4 @@
+import { useRef } from "react";
 import Dialog from "@mui/material/Dialog";
 import DialogTitle from "@mui/material/DialogTitle";
 import DialogContent from "@mui/material/DialogContent";
@@ -29,15 +30,21 @@ export default function ConfirmDialog({
   confirmVariant = "primary",
   loading = false,
 }: ConfirmDialogProps) {
+  // Retain the last shown title/message so the close (fade-out) transition
+  // doesn't flash empty when the caller clears its source data (e.g. sets the
+  // selected row to null) at the same moment it closes the dialog.
+  const shown = useRef({ title, message });
+  if (isOpen) shown.current = { title, message };
+
   return (
     <Dialog
       open={isOpen}
       onClose={loading ? undefined : onClose}
       slotProps={{ paper: { sx: { borderRadius: 3 } } }}
     >
-      <DialogTitle>{title}</DialogTitle>
+      <DialogTitle>{shown.current.title}</DialogTitle>
       <DialogContent>
-        <DialogContentText>{message}</DialogContentText>
+        <DialogContentText>{shown.current.message}</DialogContentText>
       </DialogContent>
       <DialogActions sx={{ px: 3, pb: 2 }}>
         <MuiButton onClick={onClose} color="inherit" disabled={loading}>