## Why
With `instant_interrupt` enabled, new user input should reach the model without waiting for an unfinished response or stream retry backoff.
## What changed
- Interrupt request setup, response streaming, and retry backoff when user input arrives, then continue the turn with the queued input.
- Reset the WebSocket connection and continuation state after preemption so the next request sends full history.
- Drain pending input after a preempted step even when compaction leaves the estimated context above the token limit.
## Testing
Add regression coverage for WebSocket reconnection with full history, interrupted retry backoff, input queued during compaction, and yielding running code-mode calls. Add a streaming scenario that preserves completed commentary while excluding unfinished assistant text from the replacement request.
GitOrigin-RevId: b7e42b6afffbf87da15af05e0850af8579d1353f