Menu: act on a single keypress instead of waiting for Enter

Also stops Enter from quitting the menu (it used to share the quit branch with
q) and swallows the tail of an escape sequence, so one arrow key redraws once
rather than three times and never closes the menu.

src/lib/menu.sh

@@ -145,7 +145,11 @@ cau_ui_menu() {
 		printf '  [q] %s\n' "$(cau_msg "Quit")"
 		printf '\n  > '
 
-		read -r choice || { printf '\n'; return 0; }
+		# One keypress, no Enter. -s keeps the raw character out of the
+		# display so the echo below is the only thing printed, and a failing
+		# read means EOF (Ctrl-D, or a script piping input) - that quits.
+		read -rsn1 choice || { printf '\n'; return 0; }
+		printf '%s\n' "$choice"
 
 		case "$choice" in
 			1)
@@ -163,13 +167,22 @@ cau_ui_menu() {
 			3) cau_do_run --force; cau_pause ;;
 			4) cau_do_log; cau_pause ;;
 			5) cau_ui_status_conditions; cau_pause ;;
-			q|Q|'') return 0 ;;
+			q|Q) return 0 ;;
+			$'\e')
+				# Arrow keys and friends arrive as ESC [ X. Swallow the rest so
+				# one keypress does not redraw the menu three times. Escape is
+				# deliberately not a quit key: that would make a stray arrow
+				# key close the menu.
+				read -rsn2 -t 0.05 _ 2>/dev/null || true
+				;;
+			# Anything else, Enter included, just redraws.
 			*) ;;
 		esac
 	done
 }
 
 cau_pause() {
-	printf '\n  %s' "$(cau_msg "Press Enter to continue...")"
-	read -r _ || true
+	printf '\n  %s' "$(cau_msg "Press any key to continue...")"
+	read -rsn1 _ || true
+	printf '\n'
 }