fix: preserve v1 service file for rollback instead of symlinking

The previous approach deleted the v1 unit file and symlinked it to v2,
making rollback impossible. Now we just disable v1 and leave the file
on disk so users can switch back with a single command.

Also adds rollback instructions to the migration summary output.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

migrate-v2.sh

@@ -563,47 +563,22 @@ echo
 echo "$(bold 'Service switchover')"
 echo
 
-# Retire the legacy v1 service file and alias it to the v2 unit.
+# Disable the v1 service so it doesn't auto-start, but leave the unit file
-# Called after the user confirms "keep v2", or when v1 wasn't running.
+# on disk so the user can rollback with: systemctl --user start nanoclaw
 # Idempotent — safe to call multiple times.
-retire_v1_service() {
+disable_v1_service() {
-  if [ -z "$V2_SERVICE" ]; then
-    return
-  fi
-
   if [ "$PLATFORM_SERVICE" = "systemd" ]; then
-    local unit_dir="$HOME/.config/systemd/user"
+    local v1_file="$HOME/.config/systemd/user/${V1_SERVICE}.service"
-    local v1_file="$unit_dir/${V1_SERVICE}.service"
-    local v2_file="${V2_SERVICE}.service"
-
-    # Already a correct symlink — nothing to do
-    if [ -L "$v1_file" ] && [ "$(readlink "$v1_file")" = "$v2_file" ]; then
-      return
-    fi
-
-    # Only retire if the file exists (as a regular file or stale symlink)
     if [ -f "$v1_file" ] || [ -L "$v1_file" ]; then
       systemctl --user stop "$V1_SERVICE" 2>/dev/null || true
       systemctl --user disable "$V1_SERVICE" 2>/dev/null || true
-      rm -f "$v1_file"
+      step_ok "Disabled $V1_SERVICE (unit file kept for rollback)"
-      ln -s "$v2_file" "$v1_file"
-      systemctl --user daemon-reload 2>/dev/null || true
-      step_ok "Aliased $V1_SERVICE → $V2_SERVICE"
     fi
-
   elif [ "$PLATFORM_SERVICE" = "launchd" ]; then
     local v1_plist="$HOME/Library/LaunchAgents/${V1_SERVICE}.plist"
-    local v2_plist="${V2_SERVICE}.plist"
-
-    if [ -L "$v1_plist" ] && [ "$(readlink "$v1_plist")" = "$v2_plist" ]; then
-      return
-    fi
-
     if [ -f "$v1_plist" ] || [ -L "$v1_plist" ]; then
       launchctl unload "$v1_plist" 2>/dev/null || true
-      rm -f "$v1_plist"
+      step_ok "Unloaded $V1_SERVICE (plist kept for rollback)"
-      ln -s "$v2_plist" "$v1_plist"
-      step_ok "Aliased $V1_SERVICE → $V2_SERVICE"
     fi
   fi
 }
@@ -696,14 +671,14 @@ if [ "$V1_RUNNING" = "true" ]; then
       SERVICE_SWITCHED=false
     else
       step_ok "Keeping v2 service"
-      retire_v1_service
+      disable_v1_service
     fi
   else
     step_skip "Service switchover skipped"
   fi
 else
   step_skip "v1 service not running — nothing to switch"
-  retire_v1_service
+  disable_v1_service
 fi
 
 echo
@@ -735,6 +710,16 @@ echo "    $(green '✓')  Channels installed: ${SELECTED_CHANNELS[*]}"
 fi
 echo "    $(green '✓')  Container skills copied"
 echo "    $(green '✓')  Container image built"
+if [ "$SERVICE_SWITCHED" = "true" ] && [ -n "$V2_SERVICE" ]; then
+echo "    $(green '✓')  Service switched to v2 $(dim "($V2_SERVICE)")"
+echo
+echo "  $(bold 'Rollback to v1:')"
+if [ "$PLATFORM_SERVICE" = "systemd" ]; then
+echo "    $(dim '$') systemctl --user stop $V2_SERVICE && systemctl --user start $V1_SERVICE"
+elif [ "$PLATFORM_SERVICE" = "launchd" ]; then
+echo "    $(dim '$') launchctl unload ~/Library/LaunchAgents/${V2_SERVICE}.plist && launchctl load ~/Library/LaunchAgents/${V1_SERVICE}.plist"
+fi
+fi
 echo
 echo "  $(bold 'What still needs a human:')"
 if [ "$ONECLI_OK" = "false" ]; then