Costs in Runs, long replies that keep going, and replies that reconnect

The assistant now quotes costs only in Runs, never in dollars. A long reply that keeps working, for example on a canvas, is no longer cut off at five minutes, and a reply that says it will check something goes on to do it. A step that failed once and then worked is no longer shown as an error. If your connection drops while a reply is being written, the page picks it up again where it left off, and a message sent while a reply is still running stays in the box with a note instead of disappearing.