Function extract_registered_candidates 

pub fn extract_registered_candidates(
    graphs: &[SemanticOperationGraph],
    config: SemanticCandidateConfig,
) -> SemanticCandidateExtraction

Extract bounded candidate pairs for registered SOG rules.

The inverted index partitions first by the complete BuildVariant fingerprint and then by the operation-kind sequence. It therefore never reconnects independent build variants and avoids a project-wide all-pairs comparison. API names and type categories remain evidence for the rule verifier rather than becoming a lossy cross-language index key.