feat(deps): add yay as supported AUR helper alongside paru

yay uses the same -S --noconfirm interface as paru. Detection priority
is paru > yay > pacman so paru is preferred when both are present.
When installing paru itself via paru-build special, yay -S paru is
offered as a method when yay is available, in addition to the
makepkg-from-source fallback.

functions/_fish_deps_install.fish

@@ -45,9 +45,13 @@ function _fish_deps_install
                     set -a method_labels "curl installer"
                 case paru-build
                     # Only useful on Arch; skip if pacman not present
+                    if type -q yay
+                        set -a methods special-yay-paru
+                        set -a method_labels "yay -S paru"
+                    end
                     if type -q pacman
                         set -a methods special-paru
-                        set -a method_labels "build from AUR (paru)"
+                        set -a method_labels "build from AUR (makepkg)"
                     end
                 case pipx
                     if type -q pipx
@@ -106,6 +110,8 @@ function _fish_deps_install
                     if test "$bin" = starship
                         curl -sS https://starship.rs/install.sh | sh
                     end
+                case special-yay-paru
+                    yay -S --noconfirm paru
                 case special-paru
                     set -l _build_dir (mktemp -d)
                     git clone https://aur.archlinux.org/paru.git $_build_dir