The card sits in a scroll container of its own height over an empty strip of
the same, so the slide is a setScroll() delta on the laid-out tree rather than
a rebuild a frame, and the container scissors the part not yet arrived.
Drag, flick and tap-vs-scroll now live on the scrollX/scrollY flag in
ui.lua, so any scroll box pans with no app code. tree.hit returns the
deepest node by geometry and dispatch bubbles to the nearest handler,
dropping the now-unused CAPTURE flag. keyboard moves in as ui.keyboard,
and embed compiles nested lib dirs to dotted module names.
evan