CLI: cert get doesn't take over another server's saved name

Each Jarl server has its own certificate names, but a host keeps one
saved NAME.json (and, by default, one /etc/jarl/certs/NAME). Asking a
second server for the same name overwrote the first one's settings and
files, so the first certificate quietly stopped being renewed. Now that
is refused, as is a --dir holding another certificate's files;
--replace takes the name or directory over. A --dir another saved
certificate uses is always refused.

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

CHANGELOG.md

@@ -6,6 +6,8 @@ All notable changes to Jarl are documented here. The format follows
 
 ## [Unreleased]
 
+## [0.6.1] - 2026-10-20
+
 ### Added
 
 - Certificates for other hosts: `jarl cert get NAME -d DOMAIN --dir DIR
@@ -105,6 +107,11 @@ All notable changes to Jarl are documented here. The format follows
 
 ### Fixed
 
+- `jarl cert get NAME` no longer takes over a name this host has saved
+  for another Jarl server, which overwrote that certificate's settings
+  (and, with the default `--dir`, its files), so it stopped being
+  renewed. It is refused, as is a `--dir` holding another certificate's
+  files; `--replace` takes the name or directory over.
 - The "query log is off" error named a setting that doesn't exist,
   `stats.query_retention`; it's `stats.retention.queries`.
 - `jarl zone show` for a reverse zone printed only "and 1 more" under