Introduces shared seams for paginated views, D-pad reorder, media control
routing, async singletons and the device method channel, then points the
open-coded copies at them.
Also removes unused models and duplicated provider/server plumbing, folds
the twice-implemented artifact store in the server, and factors the
repeated Flutter toolchain prologue in CI into a composite action.
Skip auto-focus in touch mode to prevent ensureVisible() from fighting
TabBarView animations, and clip each tab with ClipRect to stop hub row
overflow bleeding into adjacent tabs during swipe transitions.
edde746