fix(moonarch-git): remove untracked walker theme files before upgrade

Walker theme files at /etc/xdg/walker/themes/moonarch/ were deployed
manually before the package owned them, causing pacman file conflicts
on upgrade. pre_upgrade hook now removes untracked files so pacman
can take ownership cleanly.

moonarch-git/moonarch.install

@@ -82,6 +82,14 @@ post_install() {
     echo "==> This enables services and configures firewall."
 }
 
+pre_upgrade() {
+    # Remove untracked walker theme files from pre-package manual deploys.
+    # Without this, pacman refuses to overwrite files it doesn't own.
+    if [ -d /etc/xdg/walker/themes/moonarch ] && ! pacman -Qo /etc/xdg/walker/themes/moonarch/style.css &>/dev/null; then
+        rm -rf /etc/xdg/walker/themes/moonarch
+    fi
+}
+
 post_upgrade() {
     post_install
 }