## Why
Reverse search fetched persistent history one entry at a time, making a deep or unsuccessful search require a lookup for every older entry.
## What changed
- Keep the newest-entry probe lightweight, then scan older persistent history in bounded batches.
- Cache batch results by absolute offset and preserve continuation cursors across repeated searches.
- Ignore stale responses, retry failed batch reads a bounded number of times, and restore the draft without reporting a false “no match” state when history is unavailable.
## Testing
- Cover batch continuation, caching after query changes or cancellation, stale metadata, retry exhaustion, and thread routing.
- Verify that scanning 1,024 entries uses one single-entry lookup and eight batch lookups.
GitOrigin-RevId: efc791fcbd5290050af703dd31c5c21b33240e23
Charlie Marsh
7ed19a9758