with a little bit of magic, the shield SHOULD be able to stop the star from expanding any further.

You do know what a Dyson sphere is intended for right

yes

Ok

It's a megastructure usually used to gather energy from a star, in this case it's being used to contain the star

it keeps the stream alive so yeah :/

thats why deltarune stream died.

Actually, if you create a Dyson Sphere only a mere 2k km away from an expanding about-to-be-red-giant, it would either break the Sphere, or the Sphere would compress the star, force-fusing elements until it gets so heavy that it turns into a black hole, which would end the system and possible systems out there.

It’ll work

WITH THE POWER OF MAGIC

Still.
Even if it DOES stop the star, the sphere would still decay by radiation. Ever heard of black holes? They evaporate by Hawking Radiation.
Proof?
Look on the internet.

A Dyson swarm would be way more efficient