fix(direnv): warn user if command not found (#12840)

Co-authored-by: Carlo Sala <carlosalag@protonmail.com>

plugins/direnv/direnv.plugin.zsh

@@ -1,5 +1,8 @@
-# Don't continue if direnv is not found
-command -v direnv &>/dev/null || return
+# If direnv is not found, don't continue and print a warning
+if (( ! $+commands[direnv] )); then
+  echo "Warning: direnv not found. Please install direnv and ensure it's in your PATH before using this plugin."
+  return
+fi
 
 _direnv_hook() {
   trap -- '' SIGINT;