Auto-detach when all agents in window exit

Add agent-cmd.sh wrapper that detaches the client when all panes in the
current window have exited. This allows multiple agent windows (one per
directory) while automatically returning to the shell when done with a
particular window's agents.

- remain-on-exit keeps panes alive after agent exits to check status
- Wrapper counts running panes and detaches when it's the last one

agent.sh

@@ -2,6 +2,8 @@
 
 set -e
 
+script_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+
 # Check which agent commands are available
 agents=()
 command -v claude &>/dev/null && agents+=(claude)
@@ -20,11 +22,12 @@ window_name=$dir
 
 # Create the agent session if it doesn't exist
 if ! tmux has-session -t agent; then
-  tmux new-session -ds agent -c "$dir" -n "$window_name" "${agents[0]}"
-  [ ${#agents[@]} -gt 1 ] && tmux split-window -h -t agent:0 "${agents[1]}"
+  tmux new-session -ds agent -c "$dir" -n "$window_name" "$script_dir/agent-cmd.sh" "${agents[0]}"
+  [ ${#agents[@]} -gt 1 ] && tmux split-window -h -t agent:0 "$script_dir/agent-cmd.sh" "${agents[1]}"
   # Store the directory in a window option for later matching
   tmux set-window-option -t agent @agent_dir "$dir"
   tmux set-option -t agent status off
+  tmux set-option -t agent remain-on-exit on
   tmux attach-session -t agent
   exit 0
 fi
@@ -44,8 +47,8 @@ if [ -n "$target_window" ]; then
   tmux select-window -t "$target_window"
 else
   # Create a new window with agents
-  tmux new-window -t agent -c "$dir" -n "$window_name" "${agents[0]}"
-  [ ${#agents[@]} -gt 1 ] && tmux split-window -h -t agent -c "$dir" "${agents[1]}"
+  tmux new-window -t agent -c "$dir" -n "$window_name" "$script_dir/agent-cmd.sh" "${agents[0]}"
+  [ ${#agents[@]} -gt 1 ] && tmux split-window -h -t agent -c "$dir" "$script_dir/agent-cmd.sh" "${agents[1]}"
   # Store the directory in a window option for later matching
   tmux set-window-option -t agent @agent_dir "$dir"
 fi