Centralize compacted rollout item construction (#34533)

## What changed

- Pass only compaction message and window metadata into
  `Session::replace_compacted_history`.
- Build the persisted `CompactedItem` there after assigning any missing response
  item IDs, so its replacement history matches the live history without callers
  cloning or assembling it themselves.

GitOrigin-RevId: a6106c33b6d3eef39ac0b563a50e17f6782970dc

codex-rs/core/src/compact_remote_v2.rs

@@ -4,6 +4,7 @@ use crate::Prompt;
 use crate::ResponseStream;
 use crate::client::ModelClientSession;
 use crate::client_common::ResponseEvent;
+use crate::compact::CompactedHistoryMetadata;
 use crate::compact::CompactionAnalyticsAttempt;
 use crate::compact::CompactionAnalyticsDetails;
 use crate::compact::InitialContextInjection;
@@ -33,7 +34,6 @@ use codex_protocol::items::ContextCompactionItem;
 use codex_protocol::items::TurnItem;
 use codex_protocol::models::ContentItem;
 use codex_protocol::models::ResponseItem;
-use codex_protocol::protocol::CompactedItem;
 use codex_protocol::protocol::EventMsg;
 use codex_protocol::protocol::TokenUsage;
 use codex_protocol::protocol::TruncationPolicy;
@@ -293,14 +293,6 @@ async fn run_remote_compact_task_inner_impl(
             Some(compaction_turn_context.to_turn_context_item())
         }
     };
-    let compacted_item = CompactedItem {
-        message: String::new(),
-        replacement_history: Some(new_history.clone()),
-        window_number: Some(new_window_number),
-        first_window_id: Some(new_window_ids.first_window_id.to_string()),
-        previous_window_id: new_window_ids.previous_window_id.map(|id| id.to_string()),
-        window_id: Some(new_window_ids.window_id.to_string()),
-    };
     if let Some(trace_input_history) = trace_input_history.as_deref() {
         compaction_trace.record_installed(&CompactionCheckpointTracePayload {
             input_history: trace_input_history,
@@ -312,7 +304,11 @@ async fn run_remote_compact_task_inner_impl(
         new_history,
         reference_context_item,
         world_state_baseline,
-        compacted_item,
+        CompactedHistoryMetadata {
+            message: String::new(),
+            window_number: new_window_number,
+            window_ids: new_window_ids,
+        },
     )
     .await;
     sess.recompute_token_usage(compaction_turn_context).await;