Function capability_provider_lenses 

pub fn capability_provider_lenses<'a>(
    index: &'a ProjectIndex,
    path: &Path,
) -> Vec<(&'a SiteRef, Vec<&'a SiteRef>)>

v0.127 (editor-currency slice 6): a provider-count lens per capability definition in path, as (capability def, provider def sites). The count is providers.len(); the provider sites feed the same showReferences peek the reference lens uses. Reuses the implementations relation (the impls_of edge behind go-to-implementation), so a capability with no provider yields no lens. Sorted by definition position, alongside the reference lenses.