新增任务分享/导入功能并修复只读文件保存 EPERM

- flows: writeFlowFile 覆盖写加固(清只读属性->删除后 rename->覆盖写),
  外部复制导入的只读任务文件此前导致 flows:save EPERM 崩溃
- flows: exportFlowToPath/importFlowFromPath, 分享文件为单个 FlowDefinition
  JSON(.rpaflow.json); 导入校验 schemaVersion/nodes/edges, id 冲突时生成
  imported_ 前缀新 id 绝不覆盖既有任务
- IPC: flows:export 弹保存对话框 / flows:import 弹多选打开对话框,
  失败文件逐个汇报不阻塞其余
- preload: flows.export/flows.import; shared: FlowsImportResult 类型
- TasksPage: 头部「导入任务」按钮 + 每行「分享」按钮; App 接线与 toast
- 测试: 导出/导入往返、id 冲突、非法文件原因、只读覆盖共 4 例(7/7 绿)

src/main/index.ts

@@ -1,6 +1,6 @@
 import { app, BrowserWindow, dialog, ipcMain, screen, shell } from "electron";
 import path from "node:path";
-import type { AppInfo, AppSettings, FlowDefinition, FlowSaveOptions, FlowSaveResult } from "../shared/types";
+import type { AppInfo, AppSettings, FlowDefinition, FlowSaveOptions, FlowSaveResult, FlowSummary, FlowsImportResult } from "../shared/types";
 import {
   BrowserSession,
   externalBrowserSession,
@@ -10,7 +10,7 @@ import {
 } from "./browser/session";
 import "./capabilities";
 import { catalogPath, loadCatalog } from "./catalog";
-import { createDemoFlow, createExampleFlows, createFlow, deleteFlow, getFlow, listFlows, saveFlow } from "./flows";
+import { createDemoFlow, createExampleFlows, createFlow, deleteFlow, exportFlowToPath, getFlow, importFlowFromPath, listFlows, saveFlow, SHARE_EXTENSION } from "./flows";
 import { capabilityCount, capabilityIds, setHostBridge, setSubflowSource, type HostDialogWindow } from "@rpa/core";
 import { closeBrowserSession, setMainWindowGetter, startRun, stopRun } from "./run/manager";
 import { registerOverlayIpc } from "./overlay";
@@ -214,6 +214,49 @@ function registerIpc(): void {
     deleteFlow(id);
     return true;
   });
+  ipcMain.handle("flows:export", async (_event, id: string): Promise<string | null> => {
+    if (!mainWindow) return null;
+    const flow = getFlow(id);
+    const safeName = (flow.name || "任务").replace(/[\\/:*?"<>|]/g, "_").slice(0, 60);
+    const result = await dialog.showSaveDialog(mainWindow, {
+      title: "分享任务",
+      defaultPath: `${safeName}.${SHARE_EXTENSION}.json`,
+      filters: [
+        { name: "RPA 任务分享文件", extensions: [SHARE_EXTENSION, "json"] },
+        { name: "所有文件", extensions: ["*"] }
+      ]
+    });
+    if (result.canceled || !result.filePath) return null;
+    return exportFlowToPath(id, result.filePath);
+  });
+  ipcMain.handle("flows:import", async (): Promise<FlowsImportResult> => {
+    if (!mainWindow) return { imported: [], failed: [] };
+    const result = await dialog.showOpenDialog(mainWindow, {
+      title: "导入任务",
+      properties: ["openFile", "multiSelections"],
+      filters: [
+        { name: "RPA 任务分享文件", extensions: [SHARE_EXTENSION, "json"] },
+        { name: "所有文件", extensions: ["*"] }
+      ]
+    });
+    if (result.canceled || !result.filePaths.length) return { imported: [], failed: [] };
+    const imported: FlowSummary[] = [];
+    const failed: Array<{ file: string; reason: string }> = [];
+    for (const filePath of result.filePaths) {
+      try {
+        const flow = importFlowFromPath(filePath);
+        imported.push(listFlows().find((item) => item.id === flow.id) || {
+          id: flow.id,
+          name: flow.name,
+          updatedAt: flow.meta?.updatedAt || new Date().toISOString(),
+          nodeCount: flow.nodes.length
+        });
+      } catch (error) {
+        failed.push({ file: path.basename(filePath), reason: error instanceof Error ? error.message : String(error) });
+      }
+    }
+    return { imported, failed };
+  });
 
   ipcMain.handle("dialog:open", async (_event, options: { title?: string; filters?: Electron.FileFilter[]; directories?: boolean }) => {
     if (!mainWindow) return null;