Tensor-product representation (TPR) probing

Fits a bilinear role-filler probe (score = r^T B f, with separate learned role and filler embedding matrices bound by a shared matrix B) to a real trained model's hidden states, testing whether many independent linear probe directions actually share a common low-rank factorized basis -- a compositional/binding structure claim distinct from ordinary linear probing, which fits one direction per concept with no shared-structure constraint.