bug: Fix install script

The install script failed to check if fnm binary is installed.

closes: 12173

Author: rgildein

extensions/cli/scripts/install.sh

@@ -191,7 +191,7 @@ install_node() {
         error "Failed to install fnm. Check your network connection and try again."
     fi
 
-    if [ ! -x "$FNM_INSTALL_DIR/fnm" ]; then
+    if [ ! -x "$FNM_INSTALL_DIR" ]; then
         error "fnm installation failed - binary not found at $FNM_INSTALL_DIR/fnm"
     fi