Oh, for the record I figured out why that stat() is always uncached here.  Whenever we get a directory change event, we immediately call `_clearCachedData()` on the directory in question -- which blows away cache for both that directory _and_ all its immediate children.  So in the case of a rename, we clear the cache of both the renamed item's parent dir and the renamed item itself.

Anyway, that's still a blocker for visit() since we've now lost any record of what the renamed item's children are -- and if any of the children are directories, we need to know about it.  So I think the prefix-driven `FileWatcherDomain` fix is still the only viable solution.