A separate classical-environment null

This is a physical finite classical-feedback specification: each update is a complete quantum instrument conditional on the prior classical label. It is not the wholly classical factorization (eq:classicalfactor), because the carrier is quantum.

Let ${\mathfrak{N}}_{d,L,\mathcal{U}}$ denote the resulting null class, where $\mathcal{U}$ records the schedule, access, and intervention constraints.