[Performance] Memoize isWsl results

[gonzaloriestra]

WHY are these changes introduced?

Checking for WSL environment involves a dynamic import which can be expensive if performed repeatedly, especially in high-frequency paths like analytics.

WHAT is this pull request doing?

Memoizes the result of the isWsl check in @shopify/cli-kit. Since the WSL status is constant for the duration of the process, we can safely cache the promise of the first check.
Also adds a _resetIsWsl helper for unit testing.

Expected performance impact: Reduces redundant dynamic imports and promise allocations for the is-wsl package.

How to test your changes?

CI

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 (patch for bug fixes · minor for new features · major for breaking changes) and added a changeset with pnpm changeset add

---

PR created automatically by Jules for task 14944177195766897558 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.

[github-actions]

Differences in type declarations

We detected differences in the type declarations generated by Typescript for this branch compared to the baseline ('main' branch). Please, review them to ensure they are backward-compatible. Here are some important things to keep in mind:

• Some seemingly private modules might be re-exported through public modules.
• If the branch is behind main you might see odd diffs, rebase main into this branch.

New type declarations

We found no new type declarations in this PR

Existing type declarations

packages/cli-kit/dist/public/node/system.d.ts

@@ -111,6 +111,11 @@ export declare function isCI(): boolean;
  * @returns True if the current environment is a WSL environment.
  */
 export declare function isWsl(): Promise<boolean>;
+/**
+ * Reset the memoized WSL check.
+ * This is used for testing purposes.
+ */
+export declare function _resetIsWsl(): void;
 /**
  * Check if stdin has piped data available.
  * This distinguishes between actual piped input (e.g., )