combine proposed/presented on EIP timeline

"presented" isnt a valuable distinction here if nothing else to go with it, e.g., headliners come with forum posts, etc

this is an issue we'll also need to think about in the domain representation. we now have some data about how we're using statusHistory and presentationHistory, and my gut is telling me that we're complecting by mixing responsibilities across these various "enum" types in statusHistory and presentationHistory. granularity in important, but it's questionable where that abstraction boundary should be drawn and deferred to finding details by clicking into the call and seeing the specific context (eg. do we need 'debate'?).

let's think about this based on our coding principles on the right way to keep the domain boundaries simple and drawn at the right tradeoff, and that will leak up into providing the right UX here as well. i'm still okay with duplication in the domain if it is useful and simplifying the view to the user, but let's definitely think about the modeling and UX, which may be separate concerns.

Start by reviewing how statusHistory and presentationHistory are used in the EIP timeline and domain representation. Compare the proposed and presented distinctions with the existing call context and UX, then agree on a simpler boundary. Done means the modeling decision and corresponding timeline behavior are clearly specified.