wire_shell_path's existing-setup regex required a character before PATH=, so it missed bare assignments such as Fedora's ~/.bashrc ( PATH="$HOME/.local/bin:$HOME/bin:$PATH") and Debian's ~/.profile. The installer then appended its own line to .bashrc, .profile and .bash_profile, and because Fedora's .bash_profile sources .bashrc, login shells got ~/.local/bin on PATH several times.
Match bare assignments too, and make the appended line a no-op when PATH already contains ~/.local/bin.
