feat(scripts): automate tool and AUR package installation setup

.chezmoiscripts/run_onchange_before_10-packages.sh.tmpl

@@ -28,15 +28,32 @@ aur_pkgs="{{ range .packages.arch.desktop.aur }}{{ . }} {{ end }}{{ range .packa
 {{ else -}}
 aur_pkgs="{{ range .packages.arch.aur }}{{ . }} {{ end }}"
 {{ end -}}
-if [ -n "$(echo "$aur_pkgs" | tr -d ' ')" ]; then
+# AUR names no installed package provides yet; ones already installed from a
+# sync repo (cachyos, [omarchy]) are neither rebuilt nor replaced.
+# shellcheck disable=SC2086
+aur_missing=$(pacman -T $aur_pkgs || true)
+if [ -n "$aur_missing" ]; then
+    # No AUR helper yet: take yay from a sync repo that ships it (cachyos,
+    # chaotic-aur), else build yay-bin from the AUR (makepkg refuses root).
+    if ! command -v yay >/dev/null 2>&1 && ! command -v paru >/dev/null 2>&1; then
+        if pacman -Si yay >/dev/null 2>&1; then
+            $PACMAN -S --needed --noconfirm yay
+        elif [ "$(id -u)" -ne 0 ]; then
+            install_missing git base-devel
+            yay_build=$(mktemp -d)
+            git clone --depth 1 https://aur.archlinux.org/yay-bin.git "$yay_build"
+            (cd "$yay_build" && makepkg -si --noconfirm)
+            rm -rf "$yay_build"
+        fi
+    fi
     if command -v yay >/dev/null 2>&1; then AUR="yay"
     elif command -v paru >/dev/null 2>&1; then AUR="paru"
     else AUR=""; fi
     if [ -n "$AUR" ]; then
         # shellcheck disable=SC2086
-        $AUR -S --needed --noconfirm $aur_pkgs
+        $AUR -S --needed --noconfirm $aur_missing
     else
-        echo "warning: yay/paru not found — skipping AUR packages: $aur_pkgs" >&2
+        echo "warning: no yay/paru and none could be bootstrapped — skipping AUR packages:" $aur_missing >&2
     fi
 fi