Kodaira dimension method

How kodaira_dimension was determined, joined by +:

• from_birational_type: read off from the birational type of each component.
• newton_certificate: computed independently from the Newton polytope of a hypersurface core, and agreeing with the birational type where that decides it.
• certificate_refused: the certificate ran but its hypotheses (such as nondegeneracy) did not hold, so it gave no verdict.
• empty_char0: no characteristic-0 points.
• undetermined, birational_type_timeout, not_computed: not settled.
• CONFLICT: the two routes disagree.

Full details: docs/kodaira_dimension.md.