fix(tmux): use `$...SESSION_NAME` while attaching (#10946)

plugins/tmux/tmux.plugin.zsh

@@ -73,7 +73,11 @@ function _zsh_tmux_plugin_run() {
   [[ "$ZSH_TMUX_UNICODE" == "true" ]] && tmux_cmd+=(-u)
 
   # Try to connect to an existing session.
+  if [[ -n "$ZSH_TMUX_DEFAULT_SESSION_NAME" ]]; then
+    [[ "$ZSH_TMUX_AUTOCONNECT" == "true" ]] && $tmux_cmd attach -t $ZSH_TMUX_DEFAULT_SESSION_NAME
+  else
     [[ "$ZSH_TMUX_AUTOCONNECT" == "true" ]] && $tmux_cmd attach
+  fi
 
   # If failed, just run tmux, fixing the TERM variable if requested.
   if [[ $? -ne 0 ]]; then