Persist multi-agent runtime metadata (#25721)

Stack split from #25708. Original PR intentionally left open. This
second PR persists multi-agent runtime metadata through thread creation,
rollout recording, and thread storage.

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

@@ -1019,6 +1019,7 @@ mod tests {
             thread_source: None,
             base_instructions: BaseInstructions::default(),
             dynamic_tools: Vec::new(),
+            multi_agent_version: None,
             metadata: thread_metadata(),
         }
     }