Lorentzian signature from j^2=+1

The Lorentzian / Minkowski signature is read from the split-complex hyperbolicity already earned in Book I – II. Because j^2=+1, the carrier grammar carries null directions and causal cones before an external Lorentzian metric is imposed. Light cones are therefore the causal cones of the split-complex carrier readout. The remaining bridge question is physical: whether this algebraic cone structure reproduces the full empirical Lorentzian regime.