A Second Odd Port Creates Relative Sign Not Absolute Sign
The original parity action groupoid on two sign-related entrance vacua has one isomorphism class. Its descended Boolean probes are constant, and every absolute sign separator fails descent.
Adding a second odd source object and quotienting by simultaneous sign reversal creates two relative isomorphism classes. The product of the entrance sign and reference sign is invariant and jointly faithful on those classes. Forgetting the reference collapses both classes to the original quotient.
This is a constructive categorical window only in a changed stabilizer groupoid. It creates relative sign and never recovers absolute sign. The odd reference, its preparation, discrete-gauge consistency, and its instrument remain source gates.
Evidence: research/flavor/flavor-parity-groupoid-relative-reference.md and
research/flavor/results/wp631_parity_groupoid_relative_reference.json.