This was a really refreshing take on the theme and I enjoyed the story heavy approach. Funnily, it reminds me a bit of how Metal Gear games cut to video during story. I'm also very curious how you did the video since I was under the impression Godot's video support wasn't great.
I did encounter a similar issue with the mouse not locking as the other reviewer. I entered fullscreen and it locked but then I escaped to check if there were other controls listed on the game page and the mouse didn't re-lock when I returned to fullscreen. I was able to beat it though despite not being able to turn all the way around haha. I've found with some of my older games that constantly re-locking the mouse in the FPS controller's process method helps with web exports but I'm not sure if that's the best approach.
Overall a great game and I like the ending!