Update: refuse pre-channel downgrades; doc docker restore scope

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QKxGW1raAWaqeU8WdHsMsp

bin/omarchy-cn-update

@@ -52,6 +52,14 @@ stable)
   ;;
 esac
 
+# Never move onto a tree that predates the channel mechanism: its update
+# command cannot switch back, stranding the install
+if [[ ! -f $src/bin/omarchy-cn-channel ]]; then
+  git -C "$src" checkout -q "$old"
+  echo "$channel 通道的目标发布早于通道机制，已回退；请使用 nightly 或更新的发布" >&2
+  exit 1
+fi
+
 new=$(git -C "$src" rev-parse --short HEAD)
 echo "Channel: $channel, source: $old -> $new"
 

manual/zh-cn/02-mirrors.md

@@ -32,5 +32,6 @@ omarchycn dev-mirror doctor                        # 连通性检查
 ```
 
 写入前备份到 `~/.local/state/omarchycn/backups/dev-mirror/<时间戳>/`，
-恢复：`omarchycn restore list` + `omarchycn restore config <时间戳>`。
+恢复：`omarchycn restore list` + `omarchycn restore config <时间戳>`（仅用户级文件）。
-docker 目标写 `/etc/docker/daemon.json`（需 sudo，重启 docker 生效）。
+docker 目标写 `/etc/docker/daemon.json`（需 sudo，重启 docker 生效；系统文件不参与
+自动恢复，回退用 `omarchycn dev-mirror apply official --target docker`）。