Rich README + certify/attribute methods, design.py, bundled 8-mer atlas

Ship single k=8 discriminative model (host 0.993/0.990, engineered 0.919/0.896, 5-class 0.708); breaks adversary at order 7

Replace with RC-folded multi-order spectrum (k=4,6,8) model: host 0.982, engineered 0.895, 5-class 0.65

initial upload