Greece had multiple colonies in India and there was significant cultural diffusion in BCE times.

This isn't especially relevant. It barely covered a few scraps of northwest India. Most "Indo-Greek" civilization and culture was concentrated in Bactria and Sogdiana, not those few scraps of modern-day India, and BC Indo-Greek culture was not what we'd understand to be "Vedic Indian" so much as Persian-esque.

It also wasn't exactly part of the classical hellenistic civilization we talk about as the root of the western tradition, something of which I'm sure you're fully aware, making this a moot point.

Is there evidence of a single significant Christian library from the first century?

Pagan in this case would also exclude Judaism in its many different forms, which certainly had a long written tradition by that point.