Function effective_coverage_semantics 

pub fn effective_coverage_semantics(binding: &Binding) -> EffectiveCoverage

Resolve a binding’s effective coverage semantics. A declared value wins (validation has already refused an illegal exhaustive). An undeclared value resolves per binding, not per source: all sources on enumerable media → exhaustive; at least one non-enumerable source → curated — a mixed binding can only honestly claim the weaker of its parts, because coverage is an obligation of the binding as a whole (the artifact that is measured, reported, and keyed).