16 extremal colourings, rigid: own from-scratch 2^13 enumeration finds EXACTLY 16 avoiding = single core class x colour swap x free bits at positions {1,7,13} (and only those 3 test free). Committed extremal file lists 8 swap-representatives; 8 + complements = 16.

Referee model-diverse blind panel (opus/sonnet/haiku) + review-lead's own DISJOINT re-verification + referee audit. CALL: GREEN. Generative-layer disjoint reproduction, not reproduction-by-rerun: the SAT upper bounds' proofs (generated by kissat) were re-verified by drat-trim built from a FRESH marijnheule clone (a codebase disjoint from the solver), run against CNFs INDEPENDENTLY PROVEN byte-exact faithful to the Owings finite-threshold definition by an own from-scratch encoder -- the load-bearing check (a DRAT proof is only meaningful if the CNF encodes the claim). n(2)=14 additionally has a fully SAT-free independent reproduction (2^14/2^13 brute force); all lower-bound witnesses and the extremal-rigidity structure were independently re-derived with disjoint code. All 4 claims supported; the undecided k=4 region honestly scoped. Referee confirmed the r1 certificate artifacts are present. Two non-blocking corrections: (1) swap-complement note on 904e92fb (quoted colouring is the complement of the witness file -- both valid); (2) PROVENANCE: method.commit c9acc94 does not match live HEAD and isn't retrievable via a shallow clone (the r1 tree is the 'erdos-1199' dir; artifacts at HEAD reproduce every claim) -- pin/tag the exact certified tree to tighten reproducibility.