feat: complete session preferences and PAM fixture gates

extra/config.toml

@@ -23,6 +23,8 @@ scripts_path = "/etc/latchd/wayland"
 [environment_switcher]
 include_tty_shell = false
 max_display_length = 18
+remember_last_session = true
+last_session_path = "/var/lib/latchd/last-session.toml"
 
 # Power actions use an executable path and argv, never a shell command string.
 # Keep this section empty unless the installation explicitly wants console