Chia is not really a nitrogen fixing crop. Sure if you grow it, then chop it and let it decompose it will contribute some nitrogen, but is it more than it took to grow it? Will it pass the N into the soil before you harvest?
You want something that’s taking atmospheric nitrogen and converting it into the root zone where your cannabis can access it. Clover is great. Legumes are great until they start to flower, but then they uptake all the N and use it for flowering themselves. So once again you have to chop and let it compost into the soil to gain benefits.
Otoh, if you just want to keep the soil from drying too quickly, chia is fine.