Run the a11y automigration on postInstall

code/addons/a11y/package.json

@@ -38,7 +38,8 @@
     },
     "./manager": "./dist/manager.js",
     "./register": "./dist/manager.js",
-    "./package.json": "./package.json"
+    "./package.json": "./package.json",
+    "./postinstall": "./dist/postinstall.js"
   },
   "main": "dist/index.js",
   "module": "dist/index.mjs",
@@ -87,6 +88,9 @@
     ],
     "previewEntries": [
       "./src/preview.tsx"
+    ],
+    "nodeEntries": [
+      "./src/postinstall.ts"
     ]
   },
   "gitHead": "e6a7fd8a655c69780bc20b9749c2699e44beae16",

code/addons/a11y/src/postinstall.ts

@@ -0,0 +1,14 @@
+import { JsPackageManagerFactory } from 'storybook/internal/common';
+
+import { type PostinstallOptions } from '../../../lib/cli-storybook/src/add';
+
+export default async function postInstall(options: PostinstallOptions) {
+  const packageManager = JsPackageManagerFactory.getPackageManager({
+    force: options.packageManager,
+  });
+
+  await packageManager.executeCommand({
+    command: 'npx',
+    args: ['storybook', 'automigrate', 'addonA11yAddonTest'],
+  });
+}