- Layer info section was missing its 4-byte length field, causing all
subsequent offsets to shift and Photoshop to fail with 'unexpected end
of file'
- Layer channel data was ordered [R,G,B,A] with ids [-1,0,1,2], shifting
every channel by one (alpha held red, red held green, ...) - fixed to
[A,R,G,B] so id -1 is the alpha mask
- Verified: psd_tools opens the PSD, per-layer pixels match the rendered
originals with 0.000 mean difference