The Common Singlet Is an Existing Odd Reference Candidate
WP489's real common-source singlet can instantiate the categorical odd reference without adding a new field. Declaring both the down entrance and the singlet odd yields a unique parity solution with alternating left/right messenger parities.
Every entrance, connector, exit, and singlet-generated mass vertex survives. Kinetic entrance mixing and wrong-sector entrances remain forbidden. Every explicit bare messenger mass is odd, so the construction exists only on the common-singlet threshold domain.
The abstract relative sign descends under simultaneous reversal, but physical selector authority remains unproved: the complete matched amplitude may erase it through legal messenger rephasings or the two powers of the singlet mass.
Evidence: research/flavor/flavor-common-singlet-relative-parity-reference.md
and research/flavor/results/wp632_common_singlet_relative_parity_reference.json.