Thank you - running the npm command in the folder populated it !
I do not know exactly why it didn’t work but here is the magic…
Thanks again!

Thank you
Let me explain my situation
I bought a iiyama ProLite 32483HS display but its brightness is very low according to me… and the final result through the mirror
Tried to put my mirror in front of my macbook with luminosity to the top : works like a charm
I secretly hope that I did not buy this screen for nothing…
EDIT : my mirror has a 6mm width