fix: updates test to mock the getPackageManager call

[andguy95]

WHY are these changes introduced?

Two tests in upgrade.test.ts (should allow --version=next in tests and CI environments and should complete full upgrade flow with --version=next) fail in CLI because getPackageManager shells out to npm prefix, which is rejected now with "npm is no longer supported in a global context."

WHAT is this pull request doing?

Mocks getPackageManager from @shopify/cli-kit/node/node-package-manager in the upgrade test file. This prevents the test from spawning a real npm subprocess during displayUpgradeSummary. The mock uses vi.importActual to preserve all other real exports (like the PackageJson type) while only replacing the one function that shells out.

No production code is changed — the fix is test-only.

HOW to test your changes?

pnpm --filter @shopify/cli-hydrogen run test -- upgrade.test.ts

All 71 tests should pass, including the two that previously failed:

Checklist

• I've read the Contributing Guidelines
• I've considered possible cross-platform impacts (Mac, Linux, Windows)
• I've added a changeset if this PR contains user-facing or functional changes. Test changes or internal-only config changes do not require a changeset.
• I've added tests to cover my changes
• I've added or updated the documentation

[shopify]

Oxygen deployed a preview of your an-fix-upgrade-test-pnpm-global-context branch. Details:

Storefront	Status	Preview link	Deployment details	Last update (UTC)
Skeleton (skeleton.hydrogen.shop)	✅ Successful (Logs)	Preview deployment	Inspect deployment	April 24, 2026 3:23 PM

Learn more about Hydrogen's GitHub integration.

[github-actions]

We detected some changes in packages/*/package.json or packages/*/src, and there are no updates in the .changeset.
If the changes are user-facing and should cause a version bump, run pnpm run changeset add to track your changes and include them in the next release CHANGELOG.
If you are making simple updates to examples or documentation, you do not need to add a changeset.

[fredericoo]

lgtm, thanks for the fix

one nit below