Function load_cached_export_map 

pub fn load_cached_export_map(
    cache_dir: &Path,
    crate_name: &str,
    crate_version: &str,
    cap: &impl CapProvider<FsRead>,
) -> Option<CrateExportMap>

Attempts to load a cached export map for a dependency crate.

Returns None if the cache is missing, stale, or corrupt. Only caches registry crates (path deps are always re-scanned).