Correct the China docs and move .cn twins in the rc repository migration

AGENTS.md

@@ -100,7 +100,7 @@ Exceptions are allowed for migration and package-helper scripts where the helper
 
 - `/etc/omarchy/region` holds `china`; no file means Global. `omarchy-region` prints the region and switches it (`omarchy region china|global`); user-facing docs live in `manual/52-china.md`.
 - `install/config/region.sh` is the one system leaf for both the ISO install (`OMARCHY_REGION`, from the configurator's `omarchy_install.region`) and the runtime switch: region file, the `default/region/china/` drop-ins it symlinks, the Rime packages, and the locale. `install/user/region.sh` runs `rime-ice-installer --asset-dir /opt/packages/rime-ice` only in the `iso-chroot` context, where the ISO bundles that data.
-- `default/region/china/pacman.sed` puts a `.omarchy.cn` twin ahead of every `.omarchy.org` server; `omarchy-refresh-pacman`, `install/post-install/pacman.sh` and `omarchy-region` apply it. Nothing in `omarchy update` or migrations may rewrite the region, the mirrors or `/etc/locale.conf`.
+- `default/region/china/pacman.sed` puts a `.omarchy.cn` twin ahead of every `.omarchy.org` server; `omarchy-refresh-pacman`, `install/post-install/pacman.sh` and `omarchy-region` apply it. Nothing in `omarchy update` or migrations may change the region or `/etc/locale.conf`, and a migration that edits an `.omarchy.org` `Server` line must edit its `.cn` twin the same way.
 - China-only menu rows carry `"when":"[[ \"$(omarchy-region)\" == \"China\" ]]"` on every row, not only the submenu, because search checks each row's own guard.
 - Chinese menu labels live in `default/omarchy/omarchy-menu.zh-cn.jsonc`, merged when `LANG` starts with `zh_CN`; give a new menu row with translatable words a label there.
 - `rime-ice-installer` is built from `omarchy-pkgs` with `omarchy-offline.patch` until it ships in the Omarchy repo.