Support paginated thread forks (#35220)

## Why

`thread/fork` rejected threads using paginated history, so they could not use the same fork workflow as legacy threads.

## What changed

- Create paginated forks by referencing a frozen source-history prefix while persisting only child-owned records in the new rollout.
- Support latest, `lastTurnId`, and `beforeTurnId` boundaries, including inherited lineage, model-context reconstruction, interruption markers, and approval-reviewer inheritance.
- Make paginated reads and occurrence search traverse referenced history while excluding source records added after the fork.
- Coordinate fork preparation with archive and delete operations, and materialize compressed rollouts before they become fork references.

## Testing

Added app-server and thread-store coverage for boundary selection, active turns, inherited reads and search, compressed lineage, and concurrent source lifecycle operations.

GitOrigin-RevId: 66052d69517d7fb97a3b7817ab77a39c5ad995fd

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

@@ -26,17 +26,22 @@ pub(super) async fn materialize_to_sqlite(
     thread_id: ThreadId,
     rollout_path: &Path,
 ) -> ThreadStoreResult<()> {
-    let start_offset = super::thread_history::next_rollout_byte_offset(store, thread_id).await?;
+    let start_offset = super::thread_history::projection_state(store, thread_id)
+        .await?
+        .map_or(0, |state| state.next_byte_offset);
     let (lines, next_offset) = read_complete_rollout_lines(rollout_path, start_offset).await?;
     // Empty valid records can still consume bytes through blank or rejected complete lines.
     if lines.is_empty() && start_offset == next_offset {
         return Ok(());
     }
-    let subagent_history_start_ordinal = codex_rollout::read_session_meta_line(rollout_path)
+    let session_meta = codex_rollout::read_session_meta_line(rollout_path)
         .await
         .map_err(thread_store_io_error)?
-        .meta
-        .subagent_history_start_ordinal;
+        .meta;
+    let initial_ordinal = session_meta
+        .history_base
+        .map_or(0, |base| base.end_ordinal_exclusive);
+    let subagent_history_start_ordinal = session_meta.subagent_history_start_ordinal;
 
     let projections = lines
         .iter()
@@ -67,6 +72,7 @@ pub(super) async fn materialize_to_sqlite(
         thread_id,
         start_offset,
         next_offset,
+        initial_ordinal,
         projections,
     )
     .await