[realvolk]

Fixes:

1. use_pty with non-tty stdin: command starts in background pgrp; foreground handoff only reaches the original pgrp, so a shell that creates its own pgrp (zsh) ends up unusable on FreeBSD/macOS #583: In exec_monitor.c, replaced tcgetpgrp() with getpgid(mc->cmnd_pid) in mon_handle_sigchld. tcgetpgrp() returns the orphaned pgrp when the child sets a new one and stops on SIGTTIN.
2. Background sudo leaves terminal settings in raw-ish state after suspend/resume #552: In exec_pty.c, made pty_cleanup unconditionally call sudo_term_restore if SFD_USERTTY is valid. Fixes a race where the tty was left in raw mode if the process wasn't in the foreground.
3. pv does not work with sudo unless use_pty is disabled #553: In exec_pty.c, use term_raw_flags for the user tty. Cleared OPOST manually on the pty leader so \r works, avoiding clobbering the saved user tty state.

Tested on Linux (Artix, x86_64) with zsh, pv, and background/foreground transitions. Needs BSD/macOS testing for #583.