Possibility to deactivate `trigger_joint_command_threshold_`

> Little outside of the scope here, but what do you think about explicitly disabling this (`trigger_joint_command_threshold_ = -1;`) unless the user sets the value. Personally I would assume it would always publish unless configured.

_Originally posted by @MarqRazz in https://github.com/ros-controls/topic_based_hardware_interfaces/pull/44#discussion_r2445624811_
            