[Performance] Memoize firstPartyDev function

[gonzaloriestra]

What is this PR?

This PR introduces memoization for the firstPartyDev function in packages/cli-kit/src/public/node/context/local.ts. This optimization caches the result of the SHOPIFY_CLI_1P_DEV environment variable check when called with the default process.env. This reduces redundant calls to isTruthy and environment lookups during CLI execution.

Why is it needed?

Performance optimization to reduce redundant environment variable lookups and string parsing in high-frequency execution paths.

How to test your changes?

CI

Checkbox

• I have read the CONTRIBUTING.md document.
• I have added/updated tests for the changes.
• I have updated the documentation (if applicable).
• I have followed the style guide.

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PR created automatically by Jules for task 9117462479887176241 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

@@ -70,6 +70,10 @@ export declare function alwaysLogMetrics(env?: NodeJS.ProcessEnv): boolean;
  * @returns True if SHOPIFY_CLI_1P is truthy.
  */
 export declare function firstPartyDev(env?: NodeJS.ProcessEnv): boolean;
+/**
+ * Resets the memoized value for the first party dev check.
+ */
+export declare function _resetFirstPartyDevCache(): void;
 /**
  * Returns true if the CLI can run the "doctor-release" command.
  *