World AABB of the chunk's meshes (f32, for future priority/culling).
Optionalappearancev19 decoded header pool shared across chunks; not a directory wire field.
Stored byte length of the chunk record (compressed length when compressed).
Byte offset of the chunk record, relative to the geometry SECTION start.
Uncompressed byte length of the chunk record.
One entry of the v13 geometry chunk directory.