Shortly after posting, I found the specific magical incantation to fix this.
What you need to do is go to your Run Configurations (Run -> Run Configurations). Select the Plug-ins tab and then hit “Add Required Plug-ins”. Apply, then Run, and it should work now.
Interestingly enough, it seems to forget this change with some regularity (bug here) and so you may need to do this often before launching 🙁