M5 review fixes: key download step, honest update paths, ordered checklist, channel semantics

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

bin/omarchy-cn-update

@@ -19,10 +19,41 @@ if [[ ! -d $src/.git ]]; then
   exit 1
 fi
 
+channel=$(omarchy-cn-channel)
+channel=${channel%% *}
+
 old=$(git -C "$src" rev-parse --short HEAD)
-git -C "$src" pull --ff-only
+git -C "$src" fetch -q --tags origin
+
+case "$channel" in
+nightly)
+  git -C "$src" checkout -q quattro
+  git -C "$src" pull --ff-only origin quattro
+  ;;
+beta)
+  tag=$(git -C "$src" tag -l "*-cn.*" | sort -V | tail -1)
+  if [[ -z $tag ]]; then
+    echo "beta 通道无可用发布 tag" >&2
+    exit 1
+  fi
+  git -C "$src" checkout -q "$tag"
+  ;;
+stable)
+  tag=$(git -C "$src" tag -l "*-cn.*" | grep -vE "alpha|beta|rc" | sort -V | tail -1)
+  if [[ -z $tag ]]; then
+    echo "当前尚无 stable 发布（omarchycn channel beta 可跟随预发布）" >&2
+    exit 1
+  fi
+  git -C "$src" checkout -q "$tag"
+  ;;
+*)
+  echo "Unknown channel: $channel" >&2
+  exit 1
+  ;;
+esac
+
 new=$(git -C "$src" rev-parse --short HEAD)
-echo "Source: $old -> $new"
+echo "Channel: $channel, source: $old -> $new"
 
 "$src/bin/omarchy-cn-install-overlay"