The timeline stops losing items when it is full

The timeline caps a single read so it stays readable, and until now a full read quietly dropped its newest items while telling the reader to carry on from the end of the window. An agent reading on its pointer lost them for good. A capped read now stops just before the first item it left out and says so: has_more is true, next_cursor picks up exactly there, and the read pointer only moves that far. Each item also says when Elixir saw it as well as when it happened, since a poll can notice a promotion hours after the battle. A quiet streak is described as it was at the moment it crossed, not days later. And a week before the moment record began is no longer described as a quiet week. Contract 6.25.0.