feat(annotation): 添加切换段落时自动保存功能

- 在 LabelStudioTextEditor 组件中新增 Switch 组件用于控制自动保存
- 添加 autoSaveOnSwitch 状态管理自动保存开关
- 修改 confirmSaveBeforeSwitch 函数支持保存、放弃、取消三种决策
- 实现自动保存逻辑，当开关开启时直接保存而不弹出确认对话框
- 在段落导航栏添加自动保存开关和标签显示
- 更新切换段落时的未保存更改处理逻辑

frontend/src/pages/DataAnnotation/Annotate/LabelStudioTextEditor.tsx

@@ -1,5 +1,5 @@
 import { useCallback, useEffect, useMemo, useRef, useState } from "react";
-import { App, Button, Card, List, Spin, Typography, Tag } from "antd";
+import { App, Button, Card, List, Spin, Typography, Tag, Switch } from "antd";
 import { LeftOutlined, ReloadOutlined, SaveOutlined, MenuFoldOutlined, MenuUnfoldOutlined, CheckOutlined } from "@ant-design/icons";
 import { useNavigate, useParams } from "react-router";
 
@@ -71,6 +71,8 @@ type ExportPayload = {
   requestId?: string | null;
 };
 
+type SwitchDecision = "save" | "discard" | "cancel";
+
 const LSF_IFRAME_SRC = "/lsf/lsf.html";
 
 const resolveSegmentIndex = (value: unknown) => {
@@ -160,6 +162,7 @@ export default function LabelStudioTextEditor() {
   const [tasks, setTasks] = useState<EditorTaskListItem[]>([]);
   const [selectedFileId, setSelectedFileId] = useState<string>("");
   const [sidebarCollapsed, setSidebarCollapsed] = useState(false);
+  const [autoSaveOnSwitch, setAutoSaveOnSwitch] = useState(false);
 
   // 分段相关状态
   const [segmented, setSegmented] = useState(false);
@@ -402,14 +405,32 @@ export default function LabelStudioTextEditor() {
   }, [iframeReady, lsReady, postToIframe]);
 
   const confirmSaveBeforeSwitch = useCallback(() => {
-    return new Promise<boolean>((resolve) => {
-      modal.confirm({
+    return new Promise<SwitchDecision>((resolve) => {
+      let resolved = false;
+      let modalInstance: { destroy: () => void } | null = null;
+      const settle = (decision: SwitchDecision) => {
+        if (resolved) return;
+        resolved = true;
+        resolve(decision);
+      };
+      const handleDiscard = () => {
+        if (modalInstance) modalInstance.destroy();
+        settle("discard");
+      };
+      modalInstance = modal.confirm({
         title: "当前段落有未保存标注",
-        content: "切换段落前请先保存当前标注。",
+        content: (
+          <div className="flex flex-col gap-2">
+            <Typography.Text>切换段落前请先保存当前标注。</Typography.Text>
+            <Button type="link" danger style={{ padding: 0, height: "auto" }} onClick={handleDiscard}>
+              放弃未保存并切换
+            </Button>
+          </div>
+        ),
         okText: "保存并切换",
         cancelText: "取消",
-        onOk: () => resolve(true),
-        onCancel: () => resolve(false),
+        onOk: () => settle("save"),
+        onCancel: () => settle("cancel"),
       });
     });
   }, [modal]);
@@ -464,10 +485,17 @@ export default function LabelStudioTextEditor() {
       const hasUnsavedChange = snapshotKey !== undefined && lastSnapshot !== undefined && latestSnapshot !== lastSnapshot;
 
       if (hasUnsavedChange) {
-        const shouldSave = await confirmSaveBeforeSwitch();
-        if (!shouldSave) return;
-        const saved = await saveFromExport(payload);
-        if (!saved) return;
+        if (autoSaveOnSwitch) {
+          const saved = await saveFromExport(payload);
+          if (!saved) return;
+        } else {
+          const decision = await confirmSaveBeforeSwitch();
+          if (decision === "cancel") return;
+          if (decision === "save") {
+            const saved = await saveFromExport(payload);
+            if (!saved) return;
+          }
+        }
       }
 
       await initEditorForFile(selectedFileId, newIndex);
@@ -707,9 +735,16 @@ export default function LabelStudioTextEditor() {
                   </Button>
                 ))}
               </div>
-              <Tag color="blue" style={{ marginLeft: 8 }}>
-                {currentSegmentIndex + 1} / {segments.length}
-              </Tag>
+              <div className="flex items-center gap-2 ml-auto">
+                <Tag color="blue">{currentSegmentIndex + 1} / {segments.length}</Tag>
+                <Typography.Text style={{ fontSize: 12 }}>切段自动保存</Typography.Text>
+                <Switch
+                  size="small"
+                  checked={autoSaveOnSwitch}
+                  onChange={(checked) => setAutoSaveOnSwitch(checked)}
+                  disabled={segmentSwitching || saving || loadingTaskDetail || !lsReady}
+                />
+              </div>
             </div>
           )}