The plan in this document is now a protocol in the code, on
`wip/transparent-frames` in the layout experiment: what it does, what the
rig measures it at, and the two things it ran into -- what a widget's answer
is the answer to when a container is drawn in two of its own boxes in one
frame, and what `Pad` should be now that a frame passes through. Both are
Bryan's to decide and both are at the top of Next.
The frame/extent prototype's chronicle goes with it: its four findings that
still hold and its two failed hypotheses stay, the rest was a record of how
the code got to a shape it no longer has.