[Security] Harden LocalStorage file permissions

[gonzaloriestra]

This PR hardens the LocalStorage class by ensuring that the underlying configuration file is created and maintained with restricted permissions (0600). This prevents other users on the same system from reading potentially sensitive configuration data or tokens stored by the CLI.

The implementation uses chmodSync to set the mode to 0o600 during initialization and after any operation that might cause the file to be recreated (set, delete, clear).

Verification was performed by confirming that configuration files are now created with 0600 permissions on a Linux system, whereas they previously defaulted to more permissive modes (e.g., 0664). Existing unit tests for LocalStorage continue to pass.

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PR created automatically by Jules for task 18028481184274082040 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/local-storage.d.ts

@@ -41,6 +41,12 @@ export declare class LocalStorage<T extends Record<string, any>> {
      * @throws BugError if an unexpected error occurs.
      */
     clear(): void;
+    /**
+     * Ensures the configuration file has restricted permissions (0600),
+     * so it's only readable/writable by the current user.
+     * This is important because the configuration file may contain sensitive information.
+     */
+    private ensureRestrictedPermissions;
     /**
      * Handle errors from config operations.
      * If the error is permission-related, throw an AbortError with helpful hints.