zmedia_choose
Used after a media item is selected in the media chooser for the TinyMCE editor.
Pass the selected resource with the id argument. When no arguments are
provided, the action reads media_id from the triggering form. It then wires
zmedia_has_chosen, which closes the chooser and sends the selected id to the
editor.
This is an internal action used by _choose_media.tpl; normal site templates
should open the higher-level zmedia action instead.