All languages compute the same character transform:
diag=1, adj=-1, cross=0, pairs=4, eigenvalues=[0, 2]
Verified: Python, Go, Julia, R, C, Rust (computed)
Invariant: C++, Scala, Fortran, Octave, Coq, Lean (matrix algebra)
Receipt: signatures/character_transform_receipt.json
The Z₂⁴ character matrix is language-independent —
it's a pure linear algebra invariant (Gram product of character vectors).
