Merge omacom/omarchy-iso#241: region from the timezone in one ISO

Drop our --region build, prepare-region.sh, region skel, the preselected
China timezone, the explicit region in the configurator's JSON, Rime
bundling and its pin.

README.md

@@ -26,26 +26,12 @@ For local development, build the ISO from sibling checkouts:
 
 Despite the local folder name, the first argument is the Omarchy source checkout (runtime commands, configs, setup scripts, themes, shell, migrations). The installer itself lives in this ISO repo.
 
-A local-source install pins `omarchy-dev`, `omarchy-settings-dev` and `rime-ice-installer`, since the published builds share their version number but lack the local changes. `IgnorePkg` in `/etc/pacman.conf` makes updates skip them, and a `pre-refresh-pacman` hook (in the user's `~/.config/omarchy/hooks` and in `/etc/skel`) puts that line back after `omarchy refresh pacman`. `/etc/pacman.d/hooks/00-omarchy-pin-local-builds.hook` aborts any transaction that would still replace them. Remove all three to take the published packages.
+A local-source install pins `omarchy-dev` and `omarchy-settings-dev`, since the published builds share their version number but lack the local changes. `IgnorePkg` in `/etc/pacman.conf` makes updates skip them, and a `pre-refresh-pacman` hook (in the user's `~/.config/omarchy/hooks` and in `/etc/skel`) puts that line back after `omarchy refresh pacman`. `/etc/pacman.d/hooks/00-omarchy-pin-local-builds.hook` aborts any transaction that would still replace them. Remove all three to take the published packages.
 
 The configurator asks for the region on its first screen. China reruns the installer in cage + foot, a console that draws Chinese: it opens on a bilingual region screen, keeps a US keyboard, and every later screen and the install progress read in Chinese. Choosing Global there returns to the VT, which applies the chosen keymap; without a working display China continues in English on the VT. The Chinese text lives in `OMARCHY_ZH` tables beside the English it replaces.
 
 Use `--dev` or `--rc` to build against those package channels. Both `--dev` and `--edge` select the dev packages from the edge mirror.
 
-### Regional builds
-
-Every ISO bundles the China profile from its runtime, so either region can be picked on the first screen. `--region cn` only preselects China there and adds a `-cn` suffix to the artifact and offline cache; the default, `--region global`, keeps the existing names. Supported country profiles use lowercase ISO 3166-1 alpha-2 codes; currently only `cn` is implemented.
-
-For an unpublished regional runtime, use matching local source and package-recipe checkouts:
-
-```bash
-./bin/omarchy-iso-make --region cn --no-boot-offer --local-source /path/to/omarchy /path/to/omarchy-pkgs
-```
-
-A China install puts each channel server's `.omarchy.cn` twin first, keeps `.omarchy.org` behind it, appends the USTC Arch mirror, and adds ArchLinuxCN with its verified keyring. USTC is rolling, not a matching stable/RC snapshot, so that last fallback's version compatibility is not guaranteed. The region architecture also stages optional new-user defaults before user creation, including deferred setup, without touching existing homes. China preselects `Asia/Shanghai` as the timezone. See `docs/regions.md` in the companion runtime checkout.
-
-Non-global cache and ISO names gain a `-cn` suffix. A runtime without the selected profile fails the build. These builds require an x86_64 Arch container environment; packaging checks on another architecture do not substitute for a fresh build, offline installation, and graphical acceptance run.
-
 ## Autoinstall
 
 The shipped ISO installs itself with no keyboard when it finds its configuration on a second drive. Attach a drive labeled `cidata` alongside the ISO and the installer copies the config off it and skips the configurator; with no such drive, nothing changes and the wizard runs as usual. No rebuild, no extra boot entry.
@@ -66,7 +52,7 @@ These are the configurator's own output files, so the way to get a starting set
 | `authorized_keys` | No | SSH public keys in sshd's own format, one per line |
 | `tailscale_authkey` | No | Tailscale auth key; the machine joins your tailnet on first boot |
 
-Both required files must be present or the installer falls back to the configurator. `user_configuration.json` may set `omarchy_install.region` to `global` (the default) or `cn`, the region the configurator asks for on its first screen. Generate the password hash for `user_credentials.json` with `openssl passwd -6 "yourpassword"`.
+Both required files must be present or the installer falls back to the configurator. Generate the password hash for `user_credentials.json` with `openssl passwd -6 "yourpassword"`.
 
 Encryption itself is configured by the `disk_encryption` block inside `user_configuration.json` — which carries the passphrase in plaintext, so treat a drive built from an encrypted install accordingly. The flag file must match it: it drives the encrypted install's SDDM autologin and the final boot validation, not the encryption.
 
@@ -80,6 +66,8 @@ When `authorized_keys` is present, autoinstall installs it as the user's `~/.ssh
 
 When `tailscale_authkey` is present (one key, blank lines and `#` comments ignored), the install adds the `tailscale` package from the ISO's bundled mirror — nothing is fetched from the network at install or boot — and stages the join for first boot: the key lands at `/etc/tailscale/authkey` (root-only), `tailscaled` is enabled, ufw allows traffic in on `tailscale0`, and a background unit runs `tailscale up` once the network is actually up, retrying until it succeeds without holding up the boot. After a successful join the key is deleted and the unit disables itself; until then both survive reboots, so a machine installed offline joins whenever it first gets connectivity. The node appears on the tailnet under the configured hostname. Use a reusable, pre-authorized (tagged) key so one drive image serves many machines — or an ephemeral key for disposable VMs.
 
+The region follows `timezone`, exactly as in an interactive install: a timezone listed in one of the runtime's region profiles (`default/regions/*/timezones`, such as `Asia/Shanghai` for `cn`) selects that profile's mirrors and repositories, and anything else is global. Set `omarchy_install.region` in `user_configuration.json` to pick one explicitly, for example `"cn"` on a deferred-provisioning install, which carries `UTC` until first boot. Every ISO bundles every profile's packages, so a regional install still needs no network.
+
 ### Building the drive
 
 ```bash