Fix gptel-auto-scroll not working when insertion is at end of buffer

[JDNdeveloper]

Fixes #893, see issue for details.

[karthink]

Using run-at-time in the condition case makes the let binding and the condition-case ineffective, since it then runs at top level.

I moved the whole function into the run-at-time, but I'm not sure if this works as intended either. Could you test the latest version and let me know?

[JDNdeveloper]

Unfortunately that doesn't work correctly, the check of (point) needs to occur within the excursion otherwise it will just remain where the user's cursor is and not detect the inserted text has scrolled off the page. I tried this as well, but it didn't work either:

...
  (when-let* ((win (get-buffer-window (current-buffer) 'visible))
              ((not (pos-visible-in-window-p (point) win))))
    (run-at-time
     0 nil
     (lambda ()
       (condition-case nil
           (let ((scroll-error-top-bottom t))
             (when (window-live-p win)
               (with-selected-window win
                 (scroll-up-command))))
         (error nil))))))