feat(codex): add opt-in migration and ledger-based restore for unified session history

- Enable dialog gains a checkbox (default off) to migrate existing
  official sessions from the built-in "openai" bucket into the shared
  "custom" bucket, with per-generation backups; failed migrations retry
  at startup
- Disable dialog offers a precise restore driven by the backup ledger:
  only sessions recorded as "openai" in backups are flipped back, and
  sessions created while the toggle was on are never touched
- Completion marker and backup generations are bound to the canonical
  Codex config dir; migrate/restore serialize on an op lock and the
  marker is written conditionally inside the settings write lock
- save_settings rolls back the toggle and fails the save when the live
  rewrite fails; migration additionally requires the live config to
  actually route to the shared bucket (skips with live_not_unified so
  refused injection or proxy takeover can't split history)
- Restore refuses to run while the toggle is (re-)enabled and reports
  nothing_to_restore instead of a zero-count success; local migration
  markers are now backend-owned in merge_settings_for_save so stale
  frontend payloads can't resurrect them
- Settings autosave reverts optimistic form state on failure so a
  failed toggle change can't be replayed by an unrelated save
- ConfirmDialog supports an optional checkbox; all four locales updated

src/components/ConfirmDialog.tsx

@@ -1,3 +1,4 @@
+import { useEffect, useState } from "react";
 import {
   Dialog,
   DialogContent,
@@ -7,6 +8,7 @@ import {
   DialogTitle,
 } from "@/components/ui/dialog";
 import { Button } from "@/components/ui/button";
+import { Checkbox } from "@/components/ui/checkbox";
 import { AlertTriangle, Info } from "lucide-react";
 import { useTranslation } from "react-i18next";
 
@@ -18,7 +20,10 @@ interface ConfirmDialogProps {
   cancelText?: string;
   variant?: "destructive" | "info";
   zIndex?: "base" | "nested" | "alert" | "top";
-  onConfirm: () => void;
+  /** 可选勾选项：提供 label 即显示，勾选状态经 onConfirm 参数回传 */
+  checkboxLabel?: string;
+  checkboxDefaultChecked?: boolean;
+  onConfirm: (checkboxChecked: boolean) => void;
   onCancel: () => void;
 }
 
@@ -30,10 +35,21 @@ export function ConfirmDialog({
   cancelText,
   variant = "destructive",
   zIndex = "alert",
+  checkboxLabel,
+  checkboxDefaultChecked = false,
   onConfirm,
   onCancel,
 }: ConfirmDialogProps) {
   const { t } = useTranslation();
+  const [checkboxChecked, setCheckboxChecked] = useState(
+    checkboxDefaultChecked,
+  );
+
+  useEffect(() => {
+    if (isOpen) {
+      setCheckboxChecked(checkboxDefaultChecked);
+    }
+  }, [isOpen, checkboxDefaultChecked]);
 
   const IconComponent = variant === "info" ? Info : AlertTriangle;
   const iconClass =
@@ -58,13 +74,26 @@ export function ConfirmDialog({
             {message}
           </DialogDescription>
         </DialogHeader>
+        {checkboxLabel ? (
+          <label className="flex cursor-pointer select-none items-start gap-2 px-6 pt-3">
+            <Checkbox
+              checked={checkboxChecked}
+              onCheckedChange={(value) => setCheckboxChecked(value === true)}
+              className="mt-0.5"
+            />
+            <span className="text-sm leading-relaxed">{checkboxLabel}</span>
+          </label>
+        ) : null}
         <DialogFooter className="flex gap-2 border-t-0 bg-transparent pt-2 sm:justify-end">
           <Button variant="outline" onClick={onCancel}>
             {cancelText || t("common.cancel")}
           </Button>
           <Button
             variant={variant === "info" ? "default" : "destructive"}
-            onClick={onConfirm}
+            onClick={() =>
+              // 未渲染勾选框时不得回传 defaultChecked 残留值
+              onConfirm(checkboxLabel ? checkboxChecked : false)
+            }
           >
             {confirmText || t("common.confirm")}
           </Button>