Fix the negative-caching warning and show warnings in the CLI

The soa_warning for negative caching fired on the SOA minimum alone and
blamed BIND's resolver cap (max-ncache-ttl), which doesn't apply to an
authoritative zone. Resolvers cache negative answers for the smaller of
the SOA minimum and the SOA record's TTL (RFC 2308 section 5), and the
SOA record uses the zone's default TTL. The warning now uses that value,
explains the effect, and suggests the fix command (with --view when the
zone is in a view).

Also:
- Problem.String shows zone names without the trailing dot (jarld check).
- jarl prints the warnings a change introduces when it is applied or
  staged, not only on dry runs.
- jarl check/resync print only named-checkconf errors, not its
  "loaded serial" lines.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/validation.md

@@ -50,7 +50,7 @@ showing them.
 | `rrset_too_large`, `too_many_types` | error | BIND 9.20's limits: 100 records per RRset (`max-records-per-type`), 100 types per name (`max-types-per-name`) |
 | `spf_multiple`, `dmarc_multiple`, `dmarc_name` | warning | More than one SPF or DMARC policy (receivers then ignore them), or DMARC outside `_dmarc.` |
 | `wildcard_unusual` | warning | Wildcard NS records |
-| `soa_invalid`, `soa_warning`, `ttl_invalid` | error / warning | SOA fields and TTLs in range and sensible |
+| `soa_invalid`, `soa_warning`, `ttl_invalid` | error / warning | SOA fields and TTLs in range and sensible. One warning covers negative caching longer than 3 hours: resolvers cache "no such name" answers for the smaller of the SOA minimum and the zone's default TTL (RFC 2308), so a new name can stay invisible that long. 1 hour (`--minimum 3600`) is a good value |
 | `zone_name_invalid`, `zone_type_invalid`, `zone_duplicate` | error | Valid zone names and types. A zone exists once per view |
 | `zone_outside_view` | error | Once views exist, every zone must be in one (named requires this) |
 | `zone_missing_option` | error | Secondary, stub and mirror zones need `primaries` |