fix: make help tab read-only (stty -echo -icanon)

sethmux-help.sh

@@ -1,7 +1,10 @@
 #!/bin/bash
 # sethmux cheat sheet — runs in the persistent help tab
+# Read-only: all keyboard input is silently consumed
 # Redraws on terminal resize via trap
 
+stty -echo -icanon 2>/dev/null
+
 draw() {
   clear
   COLS=$(tput cols)
@@ -75,5 +78,5 @@ draw() {
 trap draw WINCH
 draw
 
-# Stay alive, redraw on resize
-while true; do sleep 86400; done
+# Read-only: consume all stdin silently, redraw on resize
+while IFS= read -r -s -n 1 -t 86400 _ 2>/dev/null; do :; done