Previously the libghostty-vt stream handler dropped .report_pwd as a no-op, so embedders never saw shell-reported cwd changes and the terminal's pwd field was never populated from escape sequences. Wire the action to setPwd and expose a pwd_changed callback analogous to title_changed via GHOSTTY_TERMINAL_OPT_PWD_CHANGED. The payload is passed through unparsed; embedders read it with ghostty_terminal_get and decode any URI scheme themselves.