This doesn’t get double slashes. That tells the compiler to ignore everything after //, so you’ve no prop file defined.
Just make it
#include "../props/saber_fett263_buttons.h"
Secondly, using the fett263 prop (or just in general) you’ll want to append a voicepack common folder to the font path in all of your presets, like
{"Count_TOTJ;common",
Read more here:
Default voicepacks are available here:
https://fredrik.hubbe.net/lightsaber/sound/
or custom ones here: