Computes the complimentary sector for the bath sites, i.e.
σ-s.
References syten::ProjectedPurification::complementary(), syten::hasCGC(), syten::RepRegister::Decomp::productDecomp(), syten::Basis::size(), syten::LimVec< Type, max, MaxType, type >::size(), syten::sum(), SYTEN_ASSERT, and SYTEN_ASSERT_MSG.
Referenced by syten::ProjectedPurification::complementary().