One decode_plane for raw/RLE/ZIP (decode_channel and composite), placed::eight and
quad_from for the SoLd/PlLd transforms, the writer's big-endian and UTF-16 helpers
from descriptor.rs, one delimiter const in engine_data.rs, and the dead binding in
write.rs. No behaviour change; adds ZIP and RLE composite tests.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
nonAffineTransform and the warp descriptor (named styles with bend / distortion, custom
envelope quilt meshes via ObAr meshPoints) are baked as placed over the placed bounds
(SourceLayer::placed), at up to 4x resolution.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>