What’s the most efficient way to include this javascript in only a single post?

Enqueueing scripts has not really changed, the Codex example is fine. In terms of efficiency you are talking about differences in the hundreds of milliseconds, but doing it the right way you get the benefit of the function. Even if the end user was sensitive enough to discern a page loading 0.002 seconds slower, most js is cached after the fact, so you would truly need superpowers.

You seem to be missing an action hook for your functions.php, for the sake of clarity register your scripts in separate functions or a block in the same function. For example:

function scott_highcharts(){
  //register
  wp_register_script( 'charts', get_template_directory_uri() . '/js/standalone-framework.js', array('jquery') );
  wp_register_script( 'mychart', get_template_directory_uri() . '/js/my-chart.js', array('jquery') );

  //enqueue conditional
  if ( is_page( 'test-post' )){
      wp_enqueue_script( 'charts' );
      wp_enqueue_script( 'mychart' );
  }
}
add_action( 'wp_enqueue_scripts', 'scott_highcharts' );