record the default-editor section, to come last

Asks for nano, vim or nvim and sets EDITOR/VISUAL in the shell config, plus the
Debian `editor` alternative so root and anything reading the system default agree
with it.

Has to come after the Neovim section, or nvim cannot honestly be offered as one
of the choices — which is the same ordering mistake the original made by setting
core.editor to nvim four sections before installing it.

This is the setting core.editor was left out in favour of: one preference that
git, crontab -e, visudo and systemctl edit all follow.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

scripts/setup/machine-setup/machine-setup.sh

@@ -1358,6 +1358,14 @@ fi
 #   docker · zsh + prompt (incl. .tmux.conf) · tailscale · neovim · js runtimes ·
 #   dev tools · ufw · zshrc
 #
+# And one that is new rather than ported, to come last of all:
+#
+#   default editor — ask for nano, vim or nvim and set EDITOR/VISUAL in the shell
+#   config, plus the Debian `editor` alternative so root and anything reading the
+#   system default agree with it. Has to come after Neovim is installed, or nvim
+#   cannot honestly be offered as a choice. This is the setting core.editor was
+#   deliberately left out in favour of.
+#
 # Each arrives as its own commit. Delete this block when the list is empty.