Layered qpAdm for robust ancestry

Run ancestry deconvolution in strict chronological layers (deep prehistoric, regional prehistoric, historical) and add candidate sources only when they materially improve a simpler model; stop when no improvement appears. This reduces overfitting to appealing but spurious historical labels and yields more defensible regional ancestry claims. — Provides a practical methodological fix that reduces misleading ancestry headlines and strengthens the evidentiary basis for public claims about regional origins and identity.