/**
 * Determines if the current environment is a Continuous Integration (CI) environment.
 *
 * It checks for the presence of the `CI` or `CONTINUOUS_INTEGRATION` environment variables.
 * These variables are commonly set by CI providers like GitHub Actions, Travis CI, CircleCI, etc.
 *
 * The check follows the convention that if the variable is present, it is considered true,
 * unless explicitly set to '0' or 'false' (case-sensitive for the value check, though env vars are OS dependent).
 *
 * @param env - Optional environment variables override.
 */
export declare const isCI: (env?: Record<string, string | undefined>) => boolean;