codex: migrate (more) app-server thread history reads to ThreadStore (#20575)

Migrate token usage replay, rollback responses, and detached review
setup (a special case of forking) to be served from ThreadStore reads
rather direct rollout files.

- replay restored token usage from already-loaded `RolloutItem` history
instead of reopening `Thread.path`
- rebuild rollback responses from loaded `ThreadStore` snapshots and
history
- start detached reviews from store-backed parent history and stored
review-thread metadata
- remove obsolete app-server rollout-summary helper code that became
dead after the store-backed migration
- preserve response/notification ordering for resume, fork, rollback,
and detached review flows
- add integration test coverage for the affected paths

codex-rs/thread-store/src/live_thread.rs

@@ -10,6 +10,7 @@ use crate::AppendThreadItemsParams;
 use crate::CreateThreadParams;
 use crate::LoadThreadHistoryParams;
 use crate::LocalThreadStore;
+use crate::ReadThreadParams;
 use crate::ResumeThreadParams;
 use crate::StoredThread;
 use crate::StoredThreadHistory;
@@ -140,6 +141,20 @@ impl LiveThread {
             .await
     }
 
+    pub async fn read_thread(
+        &self,
+        include_archived: bool,
+        include_history: bool,
+    ) -> ThreadStoreResult<StoredThread> {
+        self.thread_store
+            .read_thread(ReadThreadParams {
+                thread_id: self.thread_id,
+                include_archived,
+                include_history,
+            })
+            .await
+    }
+
     pub async fn update_memory_mode(
         &self,
         mode: ThreadMemoryMode,