pub fn check_cache_config() -> Result<Option<&'static str>, CacheDirError>Expand description
Validate the cache configuration once, at process startup.
Returns Ok(None) when the cache is usable, or Ok(Some(reason)) when no
root resolves and caching is therefore off — the caller emits that reason
as a single warning line. An Err is an operator-configured value Harn
cannot honor and should stop the process.