ghostty: enable copy-on-select and set $TERM

modules/programs/gui/ghostty/module.nix

@@ -28,6 +28,8 @@
     resize-overlay-duration = 0s
     cursor-style-blink = false
     confirm-close-surface = false
+    copy-on-select = true
+    term = xterm-256color
 
     shell-integration = ${shell-integration}
     command = ${getExe package}