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>

CHANGELOG.md

@@ -8,6 +8,19 @@ All notable changes to Jarl are documented here. The format follows
 
 The first version, to be released as 0.1.0.
 
+### Fixed
+
+- The negative-caching warning now uses the effective negative TTL, which
+  is the smaller of the SOA minimum and the zone's default TTL (RFC 2308).
+  It explains the real effect (new names can stay invisible to resolvers
+  that already asked) and gives the command that fixes it. Before, it
+  fired on the SOA minimum alone and wrongly blamed BIND's resolver cap.
+- Problems printed by `jarld check` show zone names without the trailing dot.
+- `jarl` now shows the warnings a change introduces when it is applied or
+  staged, not only on dry runs.
+- `jarl check` and `jarl resync` print only named-checkconf errors, not its
+  "loaded serial" lines.
+
 ### Added
 
 - **jarld daemon**: REST API (`/api/v1`) and embedded web UI, with SQLite as