Conclusion

The discrete results establish the following chain:

The explicit relay supplies the separate lower bound and makes the metric lattice speed exactly $r$ on the stated substrates. Neither scheduled ancestry nor the metric envelope is identified with the minimal influence region of every channel.

The continuum problem is not a second proof of the discrete cone. It is a construction problem involving isotropic reachability, matched operational limits, a product-preserving observable realization, and calibrated frame covariance. The velocity-polytope obstruction identifies why fixed finite periodic rescaling does not solve it.

All continuum conclusions remain conditional. The coordinate-retiming calculation does not establish physical boost closure, and the unrestricted closure analyzed here is incompatible with ordinary bidirectional relays. No invariant physical speed is claimed.