✨ feat(region): put the china channel mirrors first

- ✨ omarchy now runs per-channel china replicas, so they should lead instead of trailing as a fallback
- ♻️ prepend per-channel fragments so each channel's own mirror stays the fallback
- 🔥 drop the ustc arch mirror, which was never a stable or rc snapshot replica

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QuATgjU4mnqpqSLAKMQ14g

test/shell.d/channel-test.sh

@@ -213,7 +213,7 @@ if grep -Eq $'^(link|refresh)\t' "$log_file"; then
   fail "dev refuses an empty region profile before linking or refreshing pacman" "$(cat "$log_file")"
 fi
 mkdir -p "$checkout/default/regions/cn/pacman"
-touch "$checkout/default/regions/cn/pacman/pacman.conf.append" "$checkout/default/regions/cn/pacman/mirrorlist.append"
+touch "$checkout/default/regions/cn/pacman/pacman.conf.append" "$checkout/default/regions/cn/pacman/mirrorlist-edge.prepend"
 chmod -x "$checkout/bin/omarchy-apply-pacman"
 if OMARCHY_TEST_REGION_FILE="$test_tmp/region" run_channel dev >"$test_tmp/region.out" 2>"$test_tmp/region.err"; then
   fail "dev refuses a checkout whose pacman helper cannot run"

test/shell.d/region-pacman-test.sh

@@ -27,12 +27,12 @@ pass "refresh keeps existing config file modes"
 printf 'cn\n' > "$TARGET_ROOT/etc/omarchy/region"
 for channel in stable rc edge; do
   case "$channel" in
-    stable) host=stable-mirror.omarchy.org ;;
-    rc) host=rc-mirror.omarchy.org ;;
-    edge) host=mirror.omarchy.org ;;
+    stable) host=stable-mirror.omarchy ;;
+    rc) host=rc-mirror.omarchy ;;
+    edge) host=mirror.omarchy ;;
   esac
   apply "$channel"
-  expected=$(printf 'Server = https://%s/$repo/os/$arch\nServer = https://mirrors.ustc.edu.cn/archlinux/$repo/os/$arch' "$host")
+  expected=$(printf 'Server = https://%s.cn/$repo/os/$arch\nServer = https://%s.org/$repo/os/$arch' "$host" "$host")
   [[ $(<"$TARGET_ROOT/etc/pacman.d/mirrorlist") == "$expected" ]] || fail "$channel mirror order and variables"
   {
     cat "$ROOT/default/pacman/pacman-$channel.conf"
@@ -43,7 +43,7 @@ for channel in stable rc edge; do
   cmp "$TARGET_ROOT/etc/pacman.conf.bak" "$TARGET_ROOT/etc/pacman.conf"
   cmp "$TARGET_ROOT/etc/pacman.d/mirrorlist.bak" "$TARGET_ROOT/etc/pacman.d/mirrorlist"
 done
-pass "China keeps each channel first, appends only CN defaults, and is idempotent"
+pass "China puts its channel mirror first, keeps the global one as fallback, and is idempotent"
 
 cp "$TARGET_ROOT/etc/pacman.conf" "$scratch/before.conf"
 cp "$TARGET_ROOT/etc/pacman.d/mirrorlist" "$scratch/before.mirrors"
@@ -75,8 +75,8 @@ mkdir -p "$scratch/rendered"
 "$ROOT/bin/omarchy-apply-pacman" --render rc "$scratch/rendered" "$TARGET_ROOT"
 rg -qxF 'Server = https://pkgs.omarchy.org/rc/$arch' "$scratch/rendered/pacman.conf"
 rg -qxF '[archlinuxcn]' "$scratch/rendered/pacman.conf"
-[[ $(<"$scratch/rendered/mirrorlist") == $'Server = https://rc-mirror.omarchy.org/$repo/os/$arch\nServer = https://mirrors.ustc.edu.cn/archlinux/$repo/os/$arch' ]] ||
-  fail "render keeps the channel mirror first"
+[[ $(<"$scratch/rendered/mirrorlist") == $'Server = https://rc-mirror.omarchy.cn/$repo/os/$arch\nServer = https://rc-mirror.omarchy.org/$repo/os/$arch' ]] ||
+  fail "render puts the regional channel mirror first"
 cmp "$scratch/before.conf" "$TARGET_ROOT/etc/pacman.conf"
 pass "render builds the regional channel files without touching the target"
 

test/shell.d/region-refresh-boundary-test.sh

@@ -7,7 +7,7 @@ source "$SHELL_TEST_DIR/fixtures/sudo-boundary-test.sh"
 copy_boundary_file bin/omarchy-refresh-pacman
 copy_boundary_file bin/omarchy-apply-pacman
 for file in default/pacman/pacman-rc.conf default/pacman/mirrorlist-rc \
-  default/regions/cn/pacman/pacman.conf.append default/regions/cn/pacman/mirrorlist.append; do
+  default/regions/cn/pacman/pacman.conf.append default/regions/cn/pacman/mirrorlist-rc.prepend; do
   copy_boundary_file "$file"
 done
 
@@ -63,7 +63,7 @@ PY
   printf '\n'
   cat "$ROOT/default/regions/cn/pacman/pacman.conf.append"
 } >"$boundary_tmp/expected-pacman.conf"
-cat "$ROOT/default/pacman/mirrorlist-rc" "$ROOT/default/regions/cn/pacman/mirrorlist.append" >"$boundary_tmp/expected-mirrorlist"
+cat "$ROOT/default/regions/cn/pacman/mirrorlist-rc.prepend" "$ROOT/default/pacman/mirrorlist-rc" >"$boundary_tmp/expected-mirrorlist"
 cmp -s "$boundary_tmp/expected-pacman.conf" "$SUDO_TEST_CAPTURE/etc/pacman.conf" ||
   fail "root installs the rendered China pacman.conf" "$(diff "$boundary_tmp/expected-pacman.conf" "$SUDO_TEST_CAPTURE/etc/pacman.conf" 2>&1)"
 cmp -s "$boundary_tmp/expected-mirrorlist" "$SUDO_TEST_CAPTURE/etc/pacman.d/mirrorlist" ||