Prune agent windows who's directory no longer exists

agent.sh

@@ -41,5 +41,17 @@ else
   tmux set-window-option -t agent @agent_dir "$dir"
 fi
 
+# Prune windows whose recorded directory no longer exists. This runs after the
+# current directory's window is guaranteed to exist, so the session always
+# keeps at least one live window and is never killed out from under us.
+for window_id in $(tmux list-windows -t agent -F '#{window_id}'); do
+  window_dir=$(tmux show-window-option -t "$window_id" -v @agent_dir 2>/dev/null || true)
+  # Skip windows with no recorded directory rather than risk pruning them.
+  [ -n "$window_dir" ] || continue
+  if [ ! -d "$window_dir" ]; then
+    tmux kill-window -t "$window_id" 2>/dev/null || true
+  fi
+done
+
 # Attach to the session
 tmux attach-session -t agent