eaf-pdf-viewer: switching to other frame when press any key in tear-off-window frame

[ybyygu]

Describe the bug
eaf-pdf-viewer handles key press signal incorrectly in tear-off-window frame

To Reproduce

1. open emacs with only eaf loaded

emacs -q -l init-eaf.el

2. load eaf-pdf-viewer module:

(require 'eaf)
(require 'eaf-pdf-viewer)

3. create a new frame using tear-off-window

M-x dired-jump-other-window
M-x tear-off-window

4. open a pdf file using eaf-pdf-viewer in new window (the one that teared off)

M-x eaf-open; open minif.pdf

5. scroll the pdf view using hjkl keys. It is normal at first.
6. switch to other emacs frame (or other GUI window) and then switch back
7. scroll the pdf view again using hjkl keys: now any key press will turn you back to other emacs frame automatically, meanwhile the mouse scroll behave normally.

Expected behavior
pressing hjkl keys in eaf-pdf-viewer buffer should scroll the view, but not switch to other emacs frame

Versions (please complete the following info):

• Distro and DE/WM: KDE
• Versions of Dependencies:
• M-x emacs-version: 28.2

Error logs
Please check the *eaf* buffer, if there is any error in it, paste it here.

Screenshots
the eaf I used:

[manateelazycat]

EAF not support popup frame now, any PR are welcome.

[ybyygu]

Thank you for your guide. I will learn and hack on this direction.

EAF not support popup frame now, any PR are welcome.