✨ 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

bin/omarchy-apply-pacman

@@ -53,12 +53,15 @@ else
   trap 'rm -rf "$staging"' EXIT
 fi
 cp "$OMARCHY_PATH/default/pacman/pacman-$channel.conf" "$staging/pacman.conf"
-cp "$OMARCHY_PATH/default/pacman/mirrorlist-$channel" "$staging/mirrorlist"
-if [[ $region != "global" ]]; then
+if [[ $region == "global" ]]; then
+  cp "$OMARCHY_PATH/default/pacman/mirrorlist-$channel" "$staging/mirrorlist"
+else
   profile="$OMARCHY_PATH/default/regions/$region/pacman"
   printf '\n' >> "$staging/pacman.conf"
   cat "$profile/pacman.conf.append" >> "$staging/pacman.conf"
-  cat "$profile/mirrorlist.append" >> "$staging/mirrorlist"
+  # pacman tries servers in order, so the regional mirror leads and the
+  # channel's own mirror stays as the fallback.
+  cat "$profile/mirrorlist-$channel.prepend" "$OMARCHY_PATH/default/pacman/mirrorlist-$channel" > "$staging/mirrorlist"
 fi
 [[ -z $render_dir ]] || exit 0
 

bin/omarchy-channel-set

@@ -55,10 +55,10 @@ validate_dev_region() {
   [[ -f $region_file ]] && region=$(<"$region_file")
   [[ $region == "global" ]] && return 0
 
-  # The refresh after linking needs a runnable helper and both fragments, not
-  # just a directory with the region's name.
+  # The refresh after linking needs a runnable helper and the edge fragments
+  # dev uses, not just a directory with the region's name.
   local profile="$checkout/default/regions/$region/pacman"
-  if [[ ! -x $checkout/bin/omarchy-apply-pacman || ! -r $profile/pacman.conf.append || ! -r $profile/mirrorlist.append ]]; then
+  if [[ ! -x $checkout/bin/omarchy-apply-pacman || ! -r $profile/pacman.conf.append || ! -r $profile/mirrorlist-edge.prepend ]]; then
     fail "$checkout does not support the '$region' region, so switching would drop its package repositories. Check out a branch with default/regions/$region, or remove $region_file to use global defaults."
   fi
 }