Add text element metadata to types (#9235)

Initial type tweaking PR to make the diff of
https://github.com/openai/codex/pull/9116 smaller

This should not change any behavior, just adds some fields to types

codex-rs/core/src/rollout/tests.rs

@@ -603,6 +603,8 @@ async fn test_updated_at_uses_file_mtime() -> Result<()> {
         item: RolloutItem::EventMsg(EventMsg::UserMessage(UserMessageEvent {
             message: "hello".into(),
             images: None,
+            text_elements: Vec::new(),
+            local_images: Vec::new(),
         })),
     };
     writeln!(file, "{}", serde_json::to_string(&user_event_line)?)?;