Operator application: evaluates \( \sum_i L^i W^i R^i \cdot M \) and orthogonalises against all \( O^j \).
References syten::MPS::State::lIdx, syten::MPS::State::lInt, lw, std::move(), orthoCmp, r, syten::MPS::State::rIdx, syten::MPS::State::rInt, syten::MPS::State::uIdx, syten::MPS::State::uInt, and xtxinv.