feat(remote): 实现文件下载真实进度显示

- 下载改用流式读取，计算真实进度百分比
- 通过 IPC 事件实时推送进度到前端
- 支持 Content-Length 计算下载进度

electron/main.ts

@@ -255,9 +255,9 @@ ipcMain.handle('remote-upload-file', async (_event, serverHost: string, port: nu
   }
 });
 
-ipcMain.handle('remote-download-file', async (_event, serverHost: string, port: number, fileName: string, remotePath: string, localPath: string, password?: string) => {
+ipcMain.handle('remote-download-file', async (_event, id: string, serverHost: string, port: number, fileName: string, remotePath: string, localPath: string, password?: string) => {
   try {
-    log.info('Remote download params:', { serverHost, port, fileName, remotePath, localPath, password });
+    log.info('Remote download params:', { id, serverHost, port, fileName, remotePath, localPath, password });
     
     const win = electronState.getMainWindow();
     if (!win) {
@@ -275,8 +275,12 @@ ipcMain.handle('remote-download-file', async (_event, serverHost: string, port:
       throw new Error(`Download failed: ${response.statusText}`);
     }
 
-    const buffer = await response.arrayBuffer();
+    const contentLength = response.headers.get('Content-Length');
+    if (!contentLength) {
+      throw new Error('Server did not return Content-Length');
+    }
 
+    const totalSize = parseInt(contentLength, 10);
     const targetDir = localPath || 'C:\\';
     const targetPath = path.join(targetDir, fileName);
 
@@ -284,8 +288,31 @@ ipcMain.handle('remote-download-file', async (_event, serverHost: string, port:
       fs.mkdirSync(targetDir, { recursive: true });
     }
 
-    fs.writeFileSync(targetPath, Buffer.from(buffer));
+    const fileStream = fs.createWriteStream(targetPath);
+    const reader = response.body?.getReader();
+    if (!reader) {
+      throw new Error('Failed to get response body reader');
+    }
 
+    let downloadedSize = 0;
+    const CHUNK_SIZE = 64 * 1024;
+
+    while (true) {
+      const { done, value } = await reader.read();
+      if (done) {
+        break;
+      }
+
+      if (value) {
+        downloadedSize += value.length;
+        fileStream.write(value);
+
+        const progress = Math.round((downloadedSize / totalSize) * 100);
+        win.webContents.send('download-progress', { id, progress });
+      }
+    }
+
+    fileStream.end();
     return { success: true, filePath: targetPath };
   } catch (error: any) {
     log.error('Remote download failed:', error);