Smoothness witness

A compact payload whose format depends on rs_smoothness_method. It is not the full certificate. An empty string means the result is known and the method needs no payload; NULL means nothing is stored.

• certified_singular_fiber: comma-separated primes with a certified singular fiber, e.g. 3,13. Each listed prime proves non-smoothness, but the list is not necessarily exhaustive.
• direct_integer_critical_certificate, direct_equidimensional_jacobian_certificate: empty when smooth, otherwise the comma-separated list of non-smooth primes (exhaustive).
• three_lines_deletion: e=>target_id, the deleted element and the id of the smooth target $M \setminus e$.
• simple_core: the id of the simple core.
• all other methods: empty.

For a complete list of singular primes use rs_singular_fiber_primes.

Full details: docs/realization_scheme_singularity_census.md (Section 18.1).