Refactor pkg.fish to auto-detect the system package manager via
_fish_deps_detect_pm instead of hard-requiring paru/yay. Supports
install, uninstall, and auto (toggle) modes across paru, yay, pacman,
apt, dnf, zypper, yum, brew, and pkg. Package installed-checks now use
the correct query tool per PM (pacman -Qi, dpkg -s, rpm -q, etc.).
Also adds zypper to the _fish_deps_detect_pm detection priority list.
rootiest
