Workaround kitty F3 issue

[neurocyte]

Notcurses does not recognize the F3 key correctly in kitty (and ghostty, maybe others?).

These are some workarounds I've had lying around in my local tree for a few months that resolve the issue for me. Really, really not sure about the quality and/or correctness of these fixes though. I have not spent too much time looking at the inner workings of the notcurses input layer and these changes are just enough to get it working for me.

Comments are very welcome.

[neurocyte]

This is a workaround/fix for https://github.com/dankamongmen/notcurses/issues/2720