## Why
Reviewer compaction can invalidate previously admitted transcript evidence. When a parent checkpoint is available, restarting from that checkpoint preserves the captured parent context instead of relying on a lossy reviewer summary.
## What changed
- Restart an invalidated reviewer once from the action-time parent checkpoint, within the original review deadline.
- Preserve fresh checkpoints during startup and fit review input using the existing budget selection.
- Select transcript evidence from the checkpoint actually loaded by the reviewer. Track the transcript source so cursors remain valid across legacy-history eviction and reset when the source changes.
- Resume transcript deltas after successful recovery, including authorization added after the parent checkpoint.
## Testing
Add regression coverage for checkpoint recovery, post-checkpoint authorization, resumed deltas, and stopping after one restart. Extend history tests to cover both legacy retention and parent-checkpoint reuse, and update the checkpoint-migration snapshot.
GitOrigin-RevId: bc20fb9489afaad963303beff1c79f62fa5023f7