Function resolve_document_candidate 

fn resolve_document_candidate(
    project: ProjectInstanceId,
    document_path: &str,
    selector: &str,
    document_index: &DocumentResolutionIndex<'_>,
    candidates: &ProjectResolutionRegistry,
    staged_entities: &BTreeMap<String, GraphEntity>,
    control: &IndexWorkControl,
) -> Result<DocumentResolutionOutcome, CliError>

Resolve one normalized document target through exact staged/persisted identities.