Function phase_validate_capability_exports 

pub fn phase_validate_capability_exports(
    groups: &BTreeMap<String, Vec<usize>>,
    kinds: &BTreeMap<String, UnitKind>,
    parsed: &[ParsedFile],
    unit_tables: &HashMap<String, UnitTable>,
    errors: &mut ErrorSink,
    refs: &mut RefSink,
)

Phase 6b’: validate each context/adapter’s exports capability { … } clauses (v0.15 §4.1) — every name must be a capability the unit declares and provides, with no duplicate exports. Diagnostics go into errors and export references into refs.