A login bash reads only the first of ~/.bash_profile, ~/.bash_login and
~/.profile. wire_shell_path always wrote ~/.profile and ~/.bash_profile
when present, so a user whose only login file is ~/.bash_login never saw
~/.local/bin on PATH. Treat ~/.bash_login like ~/.bash_profile: append the
guarded PATH line when the file exists, never create it (creating
~/.bash_profile would shadow it).
The test helper resolves bash by absolute path so the login-PATH tests run
on hosts without /bin/bash (NixOS).
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.
