feat: add nick name to sub-agents (#12320)

Adding random nick name to sub-agents. Used for UX

At the same time, also storing and wiring the role of the sub-agent

codex-rs/app-server/src/thread_status.rs

@@ -622,6 +622,8 @@ mod tests {
             path: None,
             cwd: PathBuf::from("/tmp"),
             cli_version: "test".to_string(),
+            agent_nickname: None,
+            agent_role: None,
             source,
             git_info: None,
             turns: Vec::new(),