/// <summary>
        /// Expands environment variables in a string using the provided dictionary of variables.
        /// Custom variables override system variables. Windows built-in expansion is also applied
        /// to handle system-defined placeholders such as %SystemRoot%.
        /// </summary>
        /// <param name="value">The string to expand.</param>
        /// <param name="variables">The dictionary of environment variables to use during expansion.</param>
        /// <returns>The expanded string.</returns>
        /// <summary>
        /// Expands environment variables in a string using the provided dictionary of variables.
        /// Custom variables override system variables. Windows built-in expansion is also applied
        /// to handle system-defined placeholders such as %SystemRoot%.
        /// </summary>
        /// <param name="value">The string to expand.</param>
        /// <param name="variables">The dictionary of environment variables to use during expansion.</param>
        /// <returns>The expanded string.</returns>
        private static string ExpandWithDictionary(string value, IDictionary<string, string?> variables)