A solid background can't reveal whether a surface that's supposed to be
translucent (breadbox/breadclip/breadsearch's full-screen overlay
windows, breadbar's alpha-blended notification/OSD surfaces) is actually
compositing as translucent — a flat color showing through a flat color
still just looks flat. Generates a diagonal rainbow gradient (full hue
sweep, via the `image` crate) sized exactly to the capture canvas and
sets it as Sway's output background instead.
Needed installing swaybg (the external helper Sway's `output ... bg`
config directive shells out to) — without it the bg command silently
no-ops and the canvas stays black, which is why the first attempt at
this looked identical to the old flat-color version.
New bread-screenshots crate captures a layer-shell surface (by namespace+pid,
to disambiguate from an already-running instance) or the whole focused
output via grim, using bread-utils::hypr/proc. bread-utils::Monitor gains a
scale field and logical_size() so output geometry accounts for HiDPI/
transform, matching breadshot's proven math. bread-utils::hypr gains
find_layer() over hyprctl layers -j.
bread-capture is a small orchestrator that drives an app's --screenshot mode
and collects the resulting PNGs; hardcoded to breadbar's two views for now.
