Stage E: approximation must preserve the question

A useful successor must declare:

1. the complete channels and complete purifications compared;

2. the reference-preserving error topology and allowance;

3. the accessible registers on both sides of the comparison;

4. a deterministic decoder and its permitted operations;

5. the common interval of geometric, access, and recovery validity;

6. any coherent receiver that turns field access into a laboratory quantum return.

Selected entropy, a prepared transfer flag, a classical two-state control, or fixed-proxy recurrence supplies none of these automatically.