Function
Available courses renders it above its heading only while the learner has
no enrollment, so it leaves the moment they join any course. Start
course opens the first video, which enrolls them (course-enrollment);
View course opens the course page.
On a phone the thumbnail and copy share a row and the actions take the full
width beneath; from md up everything sits on one line with a progress ring.
Renders nothing for a course with no video.
A slim "next up" bar, like a mini player, that tells a learner enrolled in nothing where to begin: the recommended course's first video, where it sits, and Start course.