The Three-State Framing Port Is Response-Minimal, Not Universally Invariant
The exact endpoint-reversal action on the thirty-two legal signed Moore presentations has sixteen two-element orbits. The three incidence-and-polarity classes contain respectively eight, four, and four of those orbits.
Therefore the three-state framing port is not the universal quotient for all source-invariant observations. The repeated-generator sign is an explicit endpoint-reversal invariant that the port forgets. Nevertheless the computed reflection response is constant on each of the three fibers and takes three distinct values, so the port is the minimal sufficient quotient for that specific response.
This separates source construction from observational selection: incidence constructs the port, while the response law proves its sufficiency and minimality.
Evidence:
research/strominger/the-three-state-framing-port-is-response-minimal-not-universally-invariant.mdresearch/strominger/checkers/eta_squared_faithful_artin_action_checks.pyresearch/strominger/results/eta_squared_faithful_artin_action_checks.json
Verification: sixty of sixty exact gates pass.