Record the installer's region choice during system setup

plans/omarchycn.md

@@ -13,8 +13,8 @@ Progress source of truth for the `omarchycn` branches of `omarchy`, `omarchy-iso
 
 ## Tasks
 
-- [ ] T0 Branches and this list
-- [ ] T1 China package sources (PRD 1): region state, `omarchy-region` reader, `default/region/china/pacman.sed`, applied by `omarchy-refresh-pacman` and `install/post-install/pacman.sh`; tests
+- [x] T0 Branches and this list
+- [x] T1 China package sources (PRD 1): region state, `omarchy-region` reader, `default/region/china/pacman.sed`, applied by `omarchy-refresh-pacman` and `install/post-install/pacman.sh`; tests
 - [ ] T2 Region choice in the installer (PRD 2): `omarchy_prompt_region` in `setup-form.sh`, ISO configurator screen, orchestrator passes `OMARCHY_REGION`, `install/config/region.sh` records it
 - [ ] T3 Input method (PRD 3): rime-ice-installer patch and PKGBUILD in omarchy-pkgs, IME packages in `omarchy-other.packages`, install-time package add, user step runs the installer from bundled assets, ISO build bundles assets and the package
 - [ ] T4 CJK fontconfig fix (PRD 4): rebuild PR 9693 on the current base