Regularity method

The proof route that established rs_is_regular_scheme. The payload is in rs_regularity_witness.

• empty: the empty scheme is vacuously regular (true).
• simple_disconnected_open_affine: an open subscheme of affine space (true).
• smooth: follows from smoothness over ℤ (true).
• three_lines_deletion: follows through a smooth deletion morphism from a certified regular target (true).
• direct_mixed_jacobian: Hochster–Jeffries mixed-Jacobian test at every non-smooth prime (true or false).
• direct_vertical_fiber_jacobian: a scheme living over a single prime, tested by the ordinary Jacobian criterion (true or false).
• simple_core: copied from the simple core.
• unresolved_hypersurface_mixed_jacobian, unresolved_general_mixed_jacobian, unresolved_general_precheck, unresolved_vertical_presentation: the calculation did not finish, and the value is NULL.

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