milestone 16: behavioral fixes for silent failures, locks, counters and the query log

specs/milestone-5.md

@@ -1675,7 +1675,9 @@ and the session text disagree, this section wins.
 **S1 parsers + wildcard.** `validate` counts labels before the 253-byte length check, so
 `TooManyLabels` is reachable. A hosts line with a sink address and no name is `.unsupported`.
 `||example.com` without `^` is `.wildcard` with `covers_apex = true`. `detectFormat` treats `$` as a
-marker only on non-comment lines; `||`, `@@` and element-hiding separators are matched anchored.
+marker only on non-comment lines; `||` and `@@` are matched anchored. Element-hiding separators are
+matched positionally since milestone 16 ruling 5: at offset 0 a selector must follow the separator;
+past offset 0 a domain-list character must precede it — so a `## Title` banner is not element hiding.
 `looksLikeIpLiteral` lives in `parsers.zig` and is shared with `parser_hosts.zig`.
 `wildcard.matches` is total on unvalidated input: the label splitter returns null above `max_labels`
 and `matches` returns false — no assert, because `parsers.zig` is the S9.3 fuzz root.