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/tools/src/tool_config_tests.rs

@@ -46,6 +46,7 @@ fn model_with_shell_type(shell_type: ConfigShellToolType) -> ModelInfo {
         supports_search_tool: false,
         auto_review_model_override: None,
         tool_mode: None,
+        multi_agent_version: None,
     }
 }