Add ordinals to paginated rollout records (#32332)

## Why

Paginated thread history needs durable ordering so consumers can process a rollout suffix without rebuilding all earlier history.

## What changed

- Add optional, zero-based ordinals to `RolloutLine` records in paginated rollouts while leaving legacy rollout serialization unchanged.
- Continue ordinals from the last valid record when appending or resuming, including after gaps or an incomplete tail, and reject overflow without appending.
- Add a stateless `project_rollout_line` helper that maps canonical turn lifecycle and completed-item records into thread-history change sets.

## Testing

- Cover ordinal assignment, legacy compatibility, resume and tail recovery, overflow handling, and thread-history projection for completed, failed, and interrupted turns.

GitOrigin-RevId: 3a9bb6cd2a1f674a9f154342e96e9aa3d8330781

codex-rs/cli/src/doctor/thread_inventory.rs

@@ -819,6 +819,7 @@ mod tests {
             let parsed_thread_id = ThreadId::from_string(thread_id).expect("thread id");
             let rollout_line = RolloutLine {
                 timestamp: timestamp.to_string(),
+                ordinal: None,
                 item: RolloutItem::SessionMeta(codex_protocol::protocol::SessionMetaLine {
                     meta: codex_protocol::protocol::SessionMeta {
                         session_id: parsed_thread_id.into(),