Add a quit without confirm option

[sg-qwt]

It's a bit tricky to set-process-query-on-exit-flag (add advice like below?).

(defun my-pi-no-query-on-exit (orig-fn &rest args)
  (let ((proc (apply orig-fn args)))
    (when (processp proc)
      (set-process-query-on-exit-flag proc nil))
    proc))

(advice-add 'pi-coding-agent--start-process :around #'my-pi-no-query-on-exit)

Introduce a pi-coding-agent-quit-without-confirmation opt to allow closing pi sessions without the live-process confirmation prompt is much straightforward and simpler I think.

Or maybe we should respect the builtin confirm-kill-processes?