add doctor, scheduled backups and fetch; release 0.0.12

- doctor [<name>] [--fix]: checks the system (user, programs, folders,
  zips, units and leftover copies in /etc, sandbox access to moved
  folders, journal, polkit, daemon, orphaned boot links and schedules)
  and each instance (ownership, server zip, config paths, mods, ports,
  failed starts/backups), with a fix for each. --fix applies the safe
  ones and re-checks them.
- backup enable|disable|now|list: a systemd timer per instance
  (terraria-backup@.timer, Persistent=), saving the world first, into
  /var/lib/terraria/backups/<name>/ (group-readable), pruning only
  scheduled backups. rename carries the schedule, delete removes it.
  upgrade's backups move there too.
- fetch vanilla|tmodloader [<version>] [--list] [--upgrade <name>]:
  downloads from terraria.org / tModLoader's GitHub releases, checks
  GitHub's sha256 and the zip, names it with its version.
- terractld may write /etc/systemd/system, for backup enable and
  doctor --fix over --host.
- Units, tmpfiles, packaging, completion, docs and changelog.

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

completions/bash/terractl

@@ -52,6 +52,11 @@ _terractl_instances() {
     fi
 }
 
+# Instance names here, or on remote <host> if one is given
+_terractl_any_instances() {
+    if [[ -n $1 ]]; then _terractl_remote_instances "$1"; else _terractl_instances; fi
+}
+
 # Remotes this user added with 'terractl remote add'
 _terractl_remotes() {
     local f=${TERRACTL_CONFIG_DIR:-${XDG_CONFIG_HOME:-$HOME/.config}/terractl}/remotes.json
@@ -125,7 +130,7 @@ _terractl() {
         cword=$COMP_CWORD
     fi
 
-    local commands="new list info start stop restart enable disable attach watch cmd mods upgrade reinstall fix-perms delete rename export import"
+    local commands="new list info start stop restart enable disable attach watch cmd mods upgrade reinstall fix-perms fetch backup doctor delete rename export import"
     local console="save say playing kick ban motd password time dawn noon dusk midnight settle seed version maxplayers port clear help"
 
     # terractl --host <remote> <command> ...: the same as on this host, except
@@ -149,7 +154,7 @@ _terractl() {
         return
     fi
 
-    local command=${words[1]}
+    local command=${words[1]} prev=${words[cword-1]}
     case $command in
         list|journal-access|help|-h|--help|version|-V|--version)
             return ;;
@@ -176,6 +181,36 @@ _terractl() {
                 _terractl_reply "enable disable status token revoke"
             fi
             return ;;
+        doctor)
+            # doctor [<name>] [--fix]
+            if [[ $cur == -* ]]; then _terractl_reply "--fix"; else _terractl_reply "$(_terractl_any_instances "$host")"; fi
+            return ;;
+        fetch)
+            # fetch vanilla|tmodloader [<version>|latest] [--list] [--upgrade <name>]
+            if (( cword == 2 )); then
+                _terractl_reply "vanilla tmodloader"
+            elif [[ $prev == --upgrade ]]; then
+                _terractl_reply "$(_terractl_any_instances "$host")"
+            elif [[ $cur == -* ]]; then
+                _terractl_reply "--list --upgrade"
+            else
+                _terractl_reply "latest"
+            fi
+            return ;;
+        backup)
+            # backup enable|disable|now|list <name> [--every <when>] [--keep <number>]
+            if (( cword == 2 )); then
+                _terractl_reply "enable disable now list"
+            elif (( cword == 3 )); then
+                _terractl_reply "$(_terractl_any_instances "$host")"
+            elif [[ ${words[2]} == enable ]]; then
+                case $prev in
+                    --every) _terractl_reply "daily weekly hourly monthly" ;;
+                    --keep)  ;;
+                    *)       _terractl_reply "--every --keep" ;;
+                esac
+            fi
+            return ;;
     esac
 
     if (( cword == 2 )); then