Migration from ncli

qslib is the canonical scientific layer for future ncli integration. The migration boundary is intentionally explicit because ncli and qslib may have different site ordering, basis labels, array ownership, and optimizer state.

The qslib side is ready with:

• canonical row-major geometry and little-endian packed states;
• typed weighted interactions that preserve pair identity and realized disorder;
• exact, TDVP, SSE, and versioned artifact kernels;
• an ABI3 qslib_quantum Python surface for coarse matrices, observables, ground states, and TDVP statistics.

The parent ncli repository must add and test the backend protocol before a consumer migration is complete. That protocol should select Rust or Python explicitly, preserve the existing ncli path until parity is proven, and record the adapter’s site-order, basis, dtype, and normalization conversions. qslib does not modify the separately owned ncli tree or claim parity that has not run.