Function load_content_cache 

pub fn load_content_cache(
    index: &mut Index,
    wanted: &ContentTierIdentity,
    path: &Path,
) -> Result<ContentCacheLoad>

Restore the records of a sidecar whose identity equals wanted, returning a miss for an absent, corrupt, or foreign sidecar and for one of any other identity.

Equality, not containment: a sidecar of a wider analyzer set holds metrics a narrower request did not ask for, and one produced under other analyzer versions, options, type rules, entries, or engine counts differently. An identity this index cannot hold, because it names another entry tier or type rules, restores nothing into it.

A header that fails to parse leaves index untouched. A failure later in the record stream calls Index::clear_content: every mutation after prepare_content_analysis is confined to the content tier, and a late miss must not leave a partial one. An outside caller that already holds content and then passes a corrupt sidecar therefore sees that tier wiped. In-crate loads start with content: None.