4.18 Zig-zag generativity across both ladders

The mechanism is recursively self-feeding. A richer Hyperfunction order gives the Infrafunction ladder a richer Hyperfunction state to negatively occupy. That contributes to a richer Infrafunction order. The richer Infrafunction order then supplies a genuinely new object for the next Hyperfunction level to negatively occupy.

H_n -> -H_n -> I_(n+1) -> -I_(n+1) -> H_(n+2) -> ...

Each side therefore creates richer material for the other side's next negative-dimensional step. This is why the zig-zag is generative rather than merely oscillatory: every traversal can create new typed coordinates and new emergent interaction-space.