Tightens type-checking for Transform

[Tomaz-Vieira]

Transform was missing a few type arguments that were making pyright unhappy; it was assuming that the return type of Transform.invert was Transform[Unknown].

[clbarnes]

Thanks! I know there are a bunch of wonky type annotations around conversions between different array types too. To my mind, the whole purpose of the array API should be to provide a Protocol which actually implements it, but that doesn't seem to exist (no progress on https://github.com/data-apis/array-api-typing , and https://pypi.org/project/types-array-api/ gives a lot more red squigglies than I know what to do with...); all array_namespace seems to do is completely erase all the type information.