Preserve harness metadata across conversation history (#38058)

## What changed

- Wrap response items with optional harness-owned metadata while keeping the persisted response payload shape backward compatible.
- Store compacted-history metadata in an aligned sidecar and reject malformed sidecars.
- Carry metadata through history normalization, compaction, resume, fork, truncation, migration, and rollout recording without sending it to model providers.

## Testing

- Cover legacy rollout compatibility, metadata serialization and validation, compaction retention, and resume/fork reconstruction.

GitOrigin-RevId: 17a6127c9048ff984cb4df4d97c0751a38c29f5f

codex-rs/thread-store/src/local/mod.rs

@@ -926,12 +926,15 @@ mod tests {
                     phase: Some(MessagePhase::Commentary),
                     memory_citation: None,
                 })),
-                RolloutItem::ResponseItem(ResponseItem::FunctionCallOutput {
-                    id: None,
-                    call_id: "call-1".to_string(),
-                    output: FunctionCallOutputPayload::from_text("tool output".to_string()),
-                    internal_chat_message_metadata_passthrough: None,
-                }),
+                RolloutItem::ResponseItem(
+                    ResponseItem::FunctionCallOutput {
+                        id: None,
+                        call_id: "call-1".to_string(),
+                        output: FunctionCallOutputPayload::from_text("tool output".to_string()),
+                        internal_chat_message_metadata_passthrough: None,
+                    }
+                    .into(),
+                ),
                 RolloutItem::EventMsg(EventMsg::TokenCount(
                     codex_protocol::protocol::TokenCountEvent {
                         info: None,