Point package managers at China mirrors on cn installs

npm, PyPI and uv, Go, rustup and crates.io, RubyGems and Bundler,
and Maven reach their registries slowly or not at all from China.
On a cn install, link the profile's environment, cargo and gem
drop-ins into place. A regular file the admin wrote is never
replaced; the install fails instead.

AGENTS.md

@@ -96,6 +96,11 @@ Exceptions are allowed for migration and package-helper scripts where the helper
 - Do not add `aliases` to new menu entries. Aliases are reserved for
   established alternate names users already type, kept for compatibility.
 
+# Region
+
+- `/etc/omarchy/region` holds the region the installer derived from the timezone (`cn`); no file means Global. The profile lives in `default/regions/cn/`, its contract in `docs/regions.md`.
+- `install/config/region.sh` links the `cn` developer mirrors into `/etc` and `/.cargo` and refuses to replace a regular file it did not create.
+
 # Config Structure
 
 - `config/` - default configs copied to `~/.config/`