Effect DNS Resolver Cache

A recursive resolver that caches both answers and their absence. Every uncached lookup walks root to TLD to authoritative, three hops before your app sends a byte; the cache collapses that to zero hops until the record's per-name TTL expires, so a rotated IP still propagates on the authority's schedule. NXDOMAIN is the answer nobody caches by default, so a typo'd host in a hot loop re-walks the recursion every time; negative caching (RFC 2308) stores the non-existence with its own shorter TTL. The demo: 41 lookups cost 3 upstream queries, and a nonexistent name's 31 repeats cost 3. Pinned to effect 4.0.0-beta.98.