To be clear, I'm just attempting to get a complete idea of the potential lifecycle of a proposal, which includes it being closed. I'm looking for a complete list of vote-to-close and auto-close reasons on Area 51. I've searched around, and been unable to find a this information. clearly if I was able to vote-to-close I'd be able to click the vote-to-close button, and see a list of reasons; clearly I don't have the rep to be able to do that, just pointing out that's one of the places I attempted to find the info; though I did find the info stating 2000+ rep is needed to vote-to-close.
These are the close reasons listed under each proposal.
Proposals are also subject to deletion if they receive absolutely no activity for a month or more (i.e. abandoned proposals).