Even if you do see the original research proposal (I didn't), or your supervisor gives you a big introductory talk I don't think you'll fully grasp what you're supposed to be doing for a while. I don't know how or when but I can I assure you that someday it WILL happen, then you'll be much happier that you can take control of the project and use your own ideas to push things forward. Until then, the reading is probably the best thing to do.
Think of it like a big puzzle - all the clues are in those papers! Find out which bits (you think) relate to your work, collect them all together and try to put everything you are told to do in it's place. I know that doesn't sound efficient or even sensible but I think that's what a lot of the best students have to do (the others just don't bother and never get to the stage where they're in control?)
Your supervisor probably SHOULD be trying to give you an overall view of the research, maybe they are brushing you off by telling you to 'read widely', but you can cope! From your original post I think you'd enjoy figuring things out on your own (you just don't know it yet). Finally, I do think it would be risky to ask for the proposal at such an early stage. But you could hint and see what happens, make the supervisor think it was their idea?