- latent_shape(req, model): real Wan geometry (16ch; (T-1)//4+1, H/8, W/8) on the cuda backend; toy stand-in stays on accel/cpu. - stamp_wan21_checkpoints(card, model_root): map a root (local dir or HF id) onto the 3 components' ComponentSpec.checkpoint; build_wan21_card(checkpoint_root=...) optional.