use xrandr names without dashes and prompt_hostname instead of hostname

.config/fish/config.fish

@@ -6,6 +6,6 @@ bind \cg cancel
 
 # to synch current directory betweeen Emacs an fish shell in vterm
 function fish_vterm_prompt_end;
-    printf '\e]51;A'(whoami)'@'(hostname)':'(pwd)'\e\\';
+    printf '\e]51;A'(whoami)'@'(prompt_hostname)':'(pwd)'\e\\';
 end
 function track_directories --on-event fish_prompt; fish_vterm_prompt_end; end