drum: restrict +se-blin to expected/sane blits
We only expect the two primary screen-draw blits here.
leaf+tape
::
++ se-blin :: print and newline
- |= lin=dill-blit:dill
+ |= $= lin
+ $~ [%put ~]
+ $>(?(%put %klr) dill-blit:dill)
^+ +>
:: newline means we need to redraw the prompt,
:: so update the prompt mirror accordingly.
