Interface 4: completion, deferred filters, and exact output

The source's lem:completion concerns arithmetic equalization of passing masses. Its application depends on identifying deferred implemented tests with analytical tests on the same recorded runs. Conditioning on eventual completion instead of passing prefixes would be a different argument.

There are two normalization levels in the source: first a known passing probability

then a further exact preparation with success probability $1/4$. Only after that second step are sign reflections applied SourceExactness. Thus “completion fills the remaining mass” must not be read as a classical rule that relabels every failure branch with the unknown factorization.