PASS Outer cross-ratio formula
PASS Seed inversion identity before positive square root
PASS Strictly negative cross-ratio derivative for s>0
PASS Cross-ratio under an exact non-affine projectivity
PASS Six distinct symbolic evaluation nodes
PASS All 15 two-error location patterns decoded
PASS All 15 four-erasure patterns reconstructed
PASS Three-error ambiguity between two valid affine records
PASS All six one-error projective location patterns decoded
PASS All 20 three-erasure projective patterns reconstructed
PASS Two distinct projective records can differ at exactly four nodes
PASS Two-error ambiguity for projective coordinates
PASS Six-node symmetric rule integrates degrees zero through three
PASS Degree-four obstruction integral
PASS Obstruction vanishes at four nodes and is positive at the inner pair
PASS Exact threshold s=(sqrt(5)-1)/4
PASS Threshold sine satisfies sin(3 delta)=cos(2 delta), giving delta=18 degrees
PASS At seed angle 36 degrees the four outer nodes give positive degree-five exactness
PASS Every symmetric degree-five rule has the displayed negative inner mass
PASS Malformed affine coordinate records are rejected
PASS Invalid record counts and recovery budgets are rejected
COMPLETED 21 check groups