## Why
Live paginated history retains completed assistant text even when summaries only need the latest message. Release older text for threads with persisted history while preserving full resume responses.
## What changed
- Evict superseded assistant text from live turn state while preserving corrected items and the latest assistant message.
- Restore evicted text for full resume responses from prepared history pages, fetching remaining items by ID in bounded batches. Return an error if saved text is missing.
- Only load the active turn when it belongs in the requested initial page, and use the item ID index for targeted history reads.
## Testing
Add reducer coverage for text eviction and corrected messages. Extend running-thread resume coverage to compare full and summary items with live notifications, exercise restoration when the prepared page lacks the active turn, and check missing-text errors.
GitOrigin-RevId: 3229c0cea820f117dc6331312f1e6056a8d1d52c