[Tests] Replace real-time setTimeout with fake timers in plugin-cloudflare

[gonzaloriestra]

WHY are these changes introduced?

The test suite for @shopify/plugin-cloudflare contained a test case that used a manual 250ms setTimeout to wait for a tunnel timeout to occur. This pattern is non-deterministic, slow, and can lead to flakiness in CI environments.

WHAT is this pull request doing?

This PR refactors packages/plugin-cloudflare/src/tunnel.test.ts to use Vitest's fake timers.

• Replaced the manual 250ms sleep with vi.useFakeTimers() and vi.advanceTimersByTimeAsync(250).
• Wrapped the fake timer logic in a try...finally block to ensure vi.useRealTimers() is always called, preventing global timer leakage to other tests.
• This makes the test deterministic and improves the execution time of the specific test case from ~250ms to ~5ms.

How to test your changes?

Run the unit tests for the affected package:

pnpm --filter @shopify/plugin-cloudflare run vitest run src/tunnel.test.ts

The tests should pass consistently and noticeably faster.

Duplicate check

I performed a duplicate check by searching the git logs for previous "Tester" PRs (using the Jules label and [Tests] prefix in titles).

Query: git log --grep="[Tests]" and git log --grep="Jules"
Results: No previous PRs found addressing this specific file or using this technique in this subsystem.

Checklist

• I've considered possible cross-platform impacts (Mac, Linux, Windows)
• I've considered possible documentation changes
• I've considered analytics changes to measure impact
• The change is user-facing — I've identified the correct [bump type] and added a changeset with pnpm changeset add (N/A for test-only changes)

---

PR created automatically by Jules for task 6152379681181735382 started by @gonzaloriestra

[google-labs-jules]

👋 Jules, reporting for duty! I'm here to lend a hand with this pull request.

When you start a review, I'll add a 👀 emoji to each comment to let you know I've read it. I'll focus on feedback directed at me and will do my best to stay out of conversations between you and other bots or reviewers to keep the noise down.

I'll push a commit with your requested changes shortly after. Please note there might be a delay between these steps, but rest assured I'm on the job!

For more direct control, you can switch me to Reactive Mode. When this mode is on, I will only act on comments where you specifically mention me with @jules. You can find this option in the Pull Request section of your global Jules UI settings. You can always switch back!

New to Jules? Learn more at jules.google/docs.

---

For security, I will only act on instructions from the user who triggered this task.