Delay when resuming a chat.

When using Durable Agents and have durable stream re connection, when you open a chat it types out from the beginning, slowly like it is being typed out, even though the LLM already generated the response, the processes of replaying the stream (when you refresh) is like it's being typed out again, this is more of an issue with multi-turn chat model, which is supposed to be more suitable to production solution.

Flight booking example has that issue also, i thought that i implemented something wrong with my app, but you can see it clearly in flight booking app.

https://github.com/user-attachments/assets/2d43df3b-caf6-4014-875e-bfa8e36b6b25

This basically makes it practically unusable for big chats, i notice that even when i'm not using the multi-turn chat model, i'm using it for single turns and i notice it.

Start by reproducing the delay in the flight booking example with a durable stream reconnection or refreshed multi-turn chat. Trace the stream replay entry point and compare it with the already-generated response. Done means resumed chats display stored output promptly rather than replaying it as if it were newly generated, including for large chats.