Standard variables (required for contextual links):
$classes: String of classes that can be used to style contextually through
CSS.
$title_prefix (array): An array containing additional output populated by
modules, intended to be displayed in front of the main title tag that
appears in the template.
$title_suffix (array): An array containing additional output populated by
modules, intended to be displayed after the main title tag that appears in
the template.
The above variables are a subset of those which Backdrop provides to all
templates, and they must be printed in your template file in order for
contextual links to be properly attached. For example, the core Contextual
Links module adds the renderable contextual links themselves inside
$title_suffix, so they will appear immediately after the object's title in
the HTML. (This placement is for accessibility reasons, among others.)