Snapshot of debug code (only some works currently).
From project/simple edit the new Main.scala class:
  vi src/main/scala/com/megaannum/Main.scala
Start Vimside:
  <Leader>vs
After Vimside is up, build the code:
  <Leader>vbb
Then start the debugger:
  <Leader>dd
Enter:
  com.megaannum.Main
as the class to run.
Goto some line and set a breakpoint:
  <Leader>db
That much works.
To stop be debugging session use:
  <Leader>dq
Note that be background debug Java process is NOT removed.
Do not know why at this point so you will have to kill it
manually.  Like I said, only some of it works.