fix(migration): preapprove vitest family in generated .yarnrc.yml

Yarn 4 hardened mode (auto-enabled for public-PR installs) quarantines
packages younger than `npmMinimalAgeGate`, so a freshly published vitest
pin makes `yarn install` fail for projects Vite+ creates/migrates — the
four `vp create … (yarn)` CI jobs hit this on the same-day 4.1.9 release.

Add `npmPreapprovedPackages: [vitest, '@vitest/*']` to the generated
`.yarnrc.yml` (rewriteYarnrcYml, shared by create + migrate) so the
Vite+-managed vitest family is exempt from the age gate regardless of
release age. The `@vitest/*` glob also covers the optional
`@vitest/browser-*` peers that are not in the override set. Guarded by
`!doc.has(...)` so it never clobbers a user's existing list.

Regenerates the migration-monorepo-yarn4 global snap (only fixture that
captures `.yarnrc.yml`).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: Brooooooklyn

packages/cli/snap-tests-global/migration-monorepo-yarn4/snap.txt

@@ -81,6 +81,9 @@ export default defineConfig({
 
 > cat .yarnrc.yml # check .yarnrc.yml
 nodeLinker: node-modules
+npmPreapprovedPackages:
+  - vitest
+  - '@vitest/*'
 catalog:
   vite: npm:@voidzero-dev/vite-plus-core@latest
   vitest: <semver>

packages/cli/src/migration/migrator.ts

@@ -2261,6 +2261,16 @@ function rewriteYarnrcYml(projectPath: string): void {
     if (!doc.has('nodeLinker')) {
       doc.set('nodeLinker', 'node-modules');
     }
+    // Vite+ pins the vitest family to exact, sometimes freshly published,
+    // versions. Yarn 4 hardened mode (auto-enabled for public-PR installs)
+    // quarantines packages younger than `npmMinimalAgeGate`, which makes
+    // `yarn install` fail on a just-released vitest pin. Preapprove the family
+    // so the Vite+-managed versions install regardless of release age; the
+    // `@vitest/*` glob also covers the optional `@vitest/browser-*` peers that
+    // are not in the override set.
+    if (!doc.has('npmPreapprovedPackages')) {
+      doc.set('npmPreapprovedPackages', ['vitest', '@vitest/*']);
+    }
     // catalog
     rewriteCatalog(doc);
   });