v0.4.2

• events: Compact no longer reads the events a stream keeps, and while Since moves on, Compact and Prune no longer read again on each call the events a Limit left: on a stream that keeps 100,000, a call with Limit: 1 takes 0.06 ms instead of 9 to 14 ms, and with 40,000 waiting, Limit: 10 takes 0.1 ms instead of 3. LoadUntil and StateAt read a stream no further than their position. A Compact whose Since moved back now folds the events after the compacted position that it would have left before.
• sse: Stream.Upgrade returns nil for a stream that will never move, instead of a channel made outside any testing/synctest bubble, which stopped a bubble's clock once a stream with Reconnect had been open for a minute.