[Performance] Memoize isWsl

[gonzaloriestra]

WHY are these changes introduced?

The isWsl function in packages/cli-kit/src/public/node/system.ts performs a dynamic import of the is-wsl package every time it's called. While Node.js caches module imports, memoizing the result at the application level avoids the overhead of repeated module resolution lookups and promise creation.

WHAT is this pull request doing?

This PR memoizes the isWsl function by caching the promise of the dynamic import in a module-level variable. It also adds and exports an internal _resetIsWsl function to ensure test isolation. Unit tests have been updated and expanded to verify the memoization behavior.

How to test your changes?

CI

Post-release steps

N/A

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

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PR created automatically by Jules for task 15665184249994513171 started by @gonzaloriestra

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[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 +111,10 @@ export declare function isCI(): boolean;
  * @returns True if the current environment is a WSL environment.
  */
 export declare function isWsl(): Promise<boolean>;
+/**
+ * Resets the memoized WSL check.
+ */
+export declare function _resetIsWsl(): void;
 /**
  * Check if stdin has piped data available.
  * This distinguishes between actual piped input (e.g., )