1.0.2: Let a page say how big its frame should be

A frame the panel sizes for the plugin is a frame that is wrong for half of
them. A console wants everything the window has; a settings page wants to be
as tall as its content and no taller.

Three fields, and all three only mean something for a page the plugin draws
itself, so declaring one on a declarative page is refused rather than accepted
and ignored: the panel draws those with its own components and decides how
tall they are.

height: "auto" is the one worth explaining. The frame is sandboxed out of the
panel's origin, which is what keeps a plugin's scripts away from the panel's
DOM and cookies, and it means the panel cannot measure the frame's document
either. So the front end reports its own height, and the panel clamps what it
is told and keeps a floor under it, because a plugin that never reports one
must be a page rather than an empty strip.