nixos/bash: Reset title bar when logging out of remote NixOS system

This fixes an issue where the title bar is permanently clobbered when
you SSH into a remote NixOS system and then log out.  The solution is
to reset the title bar upon logout.

nixos/modules/programs/bash/bash.nix

@@ -112,7 +112,14 @@ in
       };
 
       logout = lib.mkOption {
-        default = "";
+        # Reset the title bar when logging out.  This protects against a remote
+        # NixOS system clobbering your local terminal's title bar when you SSH
+        # into the remote NixOS system and then log out.
+        #
+        # For more details, see: https://superuser.com/a/339946
+        default = ''
+          printf '\e]0;\a'
+        '';
         description = ''
           Shell script code called during login bash shell logout.
         '';