Preserve Guardian history across thread reconstruction (#42065)

## Why

Guardian review evidence must remain available after a compacted thread is resumed or forked, while rolled-back or parent-local evidence must not grant authorization in a different context.

## What changed

- Store the bounded, model-invisible Guardian transcript alongside compacted rollout history and restore it from the newest surviving checkpoint during replay.
- Trim Guardian history at rollback boundaries, clearing it when the boundary has already been evicted.
- Preserve the checkpoint for user-initiated forks, but remove it when spawning a subagent so parent review evidence is not inherited.
- Keep the new rollout field optional for compatibility with existing compacted records and legacy readers.

## Testing

- Cover Guardian history across compaction, restart, paginated and pathless stores, user forks, rollback, bounded replay, serialization, and subagent forks.

GitOrigin-RevId: 6ab076d5e0c3aac4d6a41ebd50ba2b200c90213e

codex-rs/core/src/agent/control/spawn.rs

@@ -996,6 +996,9 @@ impl AgentControl {
                 RolloutItem::Compacted(compacted) => {
                     // This checkpoint belongs to the inherited parent prefix.
                     compacted.latest_token_usage_record = None;
+                    // Parent-local review evidence must not become the child's authorization.
+                    // Root user authorization is collected separately by the host.
+                    compacted.guardian_history = None;
                     if let Some(replacement_history) = compacted.replacement_history.as_mut() {
                         // Matches before this checkpoint cannot survive its replacement history.
                         replaced_parent_developer_instructions = false;