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/state_db_tests.rs

@@ -158,6 +158,7 @@ fn write_rollout_with_user_message(
                     base_instructions: None,
                     dynamic_tools: None,
                     memory_mode: None,
+                    multi_agent_version: None,
                 },
                 git: None,
             }),