Fix China app installs and wire the CN AI stack into Install > AI

Offline installs ship no pacman sync db, so yay resolved official
repo dependencies as AUR packages and every catalog install failed;
omarchy-cn-app-install now runs a full -Syu first (verified end to
end: WeChat builds and installs in the VM). Kimi Code gains a real
installer command reused by the harness registry, the default-agent
path, and new Install > AI entries (Kimi Code, Deep Code, AI Hub),
and the AI Hub wizard offers to launch native harnesses immediately
so their official CLI login runs, matching how Claude Code works.

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

bin/omarchy-cn-app-install

@@ -32,6 +32,11 @@ fi
 
 case "$source_type" in
 aur)
+  # Offline installs ship no sync db; yay then treats repo deps as AUR
+  if ! compgen -G "/var/lib/pacman/sync/*.db" > /dev/null; then
+    echo "首次安装：正在同步软件仓库并更新系统（pacman -Syu）……"
+    sudo pacman -Syu --noconfirm
+  fi
   omarchy-pkg-aur-add "$(jq -r '.package' <<<"$entry")"
   ;;
 webapp)