Function cleanup_stale_index_caches 

pub(crate) async fn cleanup_stale_index_caches(
    index_id: RegionIndexId,
    access_layer: &AccessLayerRef,
    cache_manager: Option<&CacheManagerRef>,
    write_cache: Option<&Arc<WriteCache>>,
)

Evicts local state for a stale index artifact.

The remote artifact may already be referenced by another region manifest because repartitioned regions share physical SST and index paths. With GC enabled, remote deletion therefore stays in the reference-aware GC lifecycle.