chore(deps): add @vscode/vsce for packaging

- 添加 @vscode/vsce@^3.9.1 依赖用于打包 VSCode 插件
- 配置 pnpm-workspace 允许构建 @vscode/vsce-sign 和 keytar
- 在 CI 脚本中添加插件打包命令

Author: CoderJackZhu

packages/vscode/package.json

@@ -214,6 +214,7 @@
     "@mindctx/core": "workspace:*",
     "@preact/signals": "^1.2",
     "@types/vscode": "^1.85.0",
+    "@vscode/vsce": "^3.9.1",
     "esbuild": "^0.20",
     "html-to-image": "^1.11.13",
     "preact": "^10.19",