feat(configure): edit every config option in the configurator

After the NetBox instances, netssh configure now opens a menu with all
sections: SSH defaults, global SSH options (jump host, host key
checking, target, address family, extra args, -o options), SSH rules,
resolver & cache (including the cache file), shortcuts & command alias,
and completion.max_results. SSH options can also be set per instance.

The wizard rebuilt the config from its own fields, so re-running it
dropped global SSH options, ssh.rules and completion.max_results from
the file. It now edits a copy of the loaded config, and save validates
SSH options and rules before writing.

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

README.md

@@ -106,8 +106,19 @@ Re-run it at any time to change settings without editing the file manually:
 netssh configure
 ```
 
-The wizard lets you add, edit, and remove named NetBox instances, then walks through SSH defaults, resolver strategies, cache TTL, and an optional command alias,
-then saves to `~/.config/netssh.yaml`.
+The wizard first lets you add, edit, and remove named NetBox instances and set SSH options per instance.
+A menu then gives access to every other setting; open only the sections you want to change and choose **Save and exit**:
+
+| Section | Settings |
+|---|---|
+| SSH defaults | `ssh.default_user`, `ssh.default_port` |
+| SSH options | `proxy_jump`, `host_key_checking`, `target`, `address_family`, `extra_args` (one per line), `options` (`Key=Value` per line) |
+| SSH rules | add, edit, remove `ssh.rules` — match by tag, instance, kind, name pattern, each with its own SSH options |
+| Resolver & cache | strategies, management subnets, interface name, cache TTL, cache file |
+| Shortcuts & command alias | domain suffixes, hyphen stripping, `shell.alias` |
+| Completion | `completion.max_results` |
+
+The result is validated and saved to `~/.config/netssh.yaml`; Ctrl+C cancels without writing.
 
 ### Manual config