over-engineering audit: remove dead code, speculative config, duplicate queues

- delete embedded community resolver snapshot (6,760 lines) + EmbeddedServers +
  DNS_SERVERS=fresh; curated resolvers are the default. Simplify Warm (no
  sampling).
- one generic internal/sample.Queue[T] replaces three near-identical
  random-sample queues (probe, pipeline, discover).
- delete unreachable index.listOpenSearch (OpenSearch is never listable).
- delete classifyCloudFront (its match is always discarded, !ResourceSpecific).
- delete probe.Probe wrapper + Describe; tests use ProbeDetailed.
- delete store.Pool(), model.SourceDNSAlias, discover.QueueLen.
- drop dead config/no-op knobs: pipeline DirectWorkers, discover MaxPerDomain,
  discover S3/GCS/DO flags, BUCKET_SCAN_DO.
~-7,000 lines (mostly the resolver snapshot), 0 deps removed, tests green.

internal/classify/classify.go

@@ -114,8 +114,6 @@ func Classify(host string) (model.Match, bool) {
 	switch {
 	case strings.HasSuffix(host, ".amazonaws.com"):
 		return classifyAWS(&s)
-	case strings.HasSuffix(host, ".cloudfront.net"):
-		return classifyCloudFront(&s)
 	case strings.HasSuffix(host, ".core.windows.net"):
 		return classifyAzureCore(&s)
 	case strings.HasSuffix(host, ".database.windows.net"):