- Prevents the % left indicator from immediately decrementing to ~97%.
- Tested by prompting "hi" and noting it only decremented to 99%. And by
adding a bunch of debug logs and observing numbers.
Introduces `EventMsg::TurnAborted` that should be sent in response to
`Op::Interrupt`.
In the MCP server, updates the handling of a
`ClientRequest::InterruptConversation` request such that it sends the
`Op::Interrupt` but does not respond to the request until it sees an
`EventMsg::TurnAborted`.
