Test the editor with Vitest: grid and top bar rules, the store, and the components in jsdom

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

web/vitest.config.ts

@@ -0,0 +1,13 @@
+import vue from "@vitejs/plugin-vue";
+import { defineConfig } from "vitest/config";
+
+// Unit and component tests of the editor: the grid rules, the top bar rules, the store and the components,
+// in jsdom. `npm test` runs them; `npm run test:watch` while developing.
+export default defineConfig({
+  plugins: [vue()],
+  test: {
+    environment: "jsdom",
+    include: ["tests/**/*.spec.ts"],
+    restoreMocks: true,
+  },
+});