Add multi-agent runtime metadata types (#25720)

Stack split from #25708. Original PR intentionally left open. This first
PR adds the multi-agent runtime metadata types and catalog plumbing used
by the rest of the stack.

codex-rs/rollout/src/compression_tests.rs

@@ -473,6 +473,7 @@ fn write_rollout(path: &std::path::Path, thread_id: ThreadId, message: &str) ->
             base_instructions: None,
             dynamic_tools: None,
             memory_mode: None,
+            multi_agent_version: None,
         },
         git: None,
     };