E0: a fixed comparison domain

No nonzero old comparison subspace carrying an explicitly supplied old time-ordered map is present in the supplied data. The only old seed space on which a map is determined without additional information is

with its unique zero map. We therefore freeze the minimal full first-stage target

This choice does not claim a nonzero old time-ordered overlap. Any actual old intersection must still be audited:

One must not infer ${\mathcal{O}}_{\mathrm{act}}=0$ merely from $D_{\mathrm{new}}\cap D_{\mathrm{old}}=0$: conjugation saturation needs its own subspace information.