A separately imposed comparison restriction

This is the bounded-segment alternative of X-Enter XEnter. It is approximate closure under a new restriction, not an exact loophole in Theorem thm:orbit.

Calling $A_{\mathrm{sig}}$ a physical signal requires independent provenance. The scalar input alone does not label one displacement as physical and another as gauge. The required signal-to-gap ratio also depends on $v$ and $\delta$; it is not an unconditional claim that the signal must exceed the gap.