[Performance] Memoize isShopify

[gonzaloriestra]

WHY are these changes introduced?

The isShopify function is called frequently, including during analytics generation for every command. It performs an asynchronous filesystem check for the presence of the dev binary. Since the environment and installation status are static during a single CLI execution, this check can be safely memoized to improve efficiency.

WHAT is this pull request doing?

• Memoizes the isShopify result when called with the default process.env.
• Caches the Promise directly to ensure concurrent calls await the same operation.
• Introduced a internal _resetIsShopifyMemo utility to maintain test isolation.
• Added a new unit test to verify that the filesystem is only queried once.

How to test your changes?

pnpm --filter @shopify/cli-kit vitest run src/public/node/context/local.test.ts

Post-release steps

None.

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 14669418771078202875 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/context/local.d.ts

@@ -33,6 +33,11 @@ export declare function isVerbose(env?: NodeJS.ProcessEnv): boolean;
  * @returns True if the CLI is used in a Shopify environment.
  */
 export declare function isShopify(env?: NodeJS.ProcessEnv): Promise<boolean>;
+/**
+ * Resets the memoized value for the Shopify check.
+ * This is only used for testing purposes.
+ */
+export declare function _resetIsShopifyMemo(): void;
 /**
  * This variable is used when running unit tests to indicate that the CLI's business logic
  * is run as a subject of a unit test. We can use this variable to disable output through