Pure helpers for HDR pixel buffer manipulation, plus the unified
render-target readback primitive readPixelsCompactAsync.
The pure helpers (half-float ↔ float32, row flip, WebGPU row-padding
compaction) are kept exported because tests cover them directly and
because readPixelsCompactAsync composes them. New call sites should
prefer readPixelsCompactAsync, which handles backend dispatch,
WebGPU padding, and canonical Y orientation in one place.
Pure helpers for HDR pixel buffer manipulation, plus the unified render-target readback primitive
readPixelsCompactAsync.The pure helpers (half-float ↔ float32, row flip, WebGPU row-padding compaction) are kept exported because tests cover them directly and because
readPixelsCompactAsynccomposes them. New call sites should preferreadPixelsCompactAsync, which handles backend dispatch, WebGPU padding, and canonical Y orientation in one place.