Use fzf to pick the agent in agent-cmd.sh

Move agent discovery out of `agent.sh` so the picker runs on every new
pane, including manual splits. Set the agent session's default-command
to agent-cmd.sh and re-apply session options on every invocation so
changes propagate to live sessions.

agent.sh

@@ -4,17 +4,6 @@ set -e
 
 script_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 
-# Check which agent commands are available
-agents=()
-command -v claude &>/dev/null && agents+=(claude)
-command -v opencode &>/dev/null && agents+=(opencode)
-command -v gemini &>/dev/null && agents+=(gemini)
-
-if [ ${#agents[@]} -eq 0 ]; then
-  echo "No agent commands found (claude, gemini)"
-  exit 1
-fi
-
 # Use the current directory (set via display-popup -d)
 dir="${PWD:-$HOME}"
 # Use the directory basename as window name
@@ -22,16 +11,16 @@ window_name=$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" "$script_dir/agent-cmd.sh" "${agents[0]}"
-  [ ${#agents[@]} -gt 1 ] && tmux split-window -h -t agent:0 "$script_dir/agent-cmd.sh" "${agents[1]}"
+  tmux new-session -ds agent -c "$dir" -n "$window_name" "$script_dir/agent-cmd.sh"
   # 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
 
+# Apply session options on every invocation so updates propagate to live sessions
+tmux set-option -t agent status off
+tmux set-option -t agent remain-on-exit on
+tmux set-option -t agent default-command "$script_dir/agent-cmd.sh"
+
 # Search for an existing window with matching directory
 target_window=""
 for window_id in $(tmux list-windows -t agent -F '#{window_id}'); do
@@ -46,9 +35,8 @@ if [ -n "$target_window" ]; then
   # Select the existing window
   tmux select-window -t "$target_window"
 else
-  # Create a new window with agents
-  tmux new-window -t agent -c "$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]}"
+  # Create a new window; default-command runs agent-cmd.sh
+  tmux new-window -t agent -c "$dir" -n "$window_name"
   # Store the directory in a window option for later matching
   tmux set-window-option -t agent @agent_dir "$dir"
 fi