Foreground-process cwd can't track directories inside tmux

To find a remote terminal's current directory, a common trick is to read the cwd of the pty's foreground process-group leader (/proc/<pgid>/cwd). Inside tmux that leader is the tmux client, whose cwd never changes, so every query returns the directory tmux started in. Detect a tmux foreground executable and skip the query, or ask tmux directly (tmux display -p '#{pane_current_path}'). Also, capping in-flight queries at one per terminal does not limit their rate when titles change faster than a round trip, e.g. spinners or per-command titles. Add a minimum gap of about 1 s between query starts, plus one trailing query.