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/tui/src/chatwidget.rs

@@ -2266,7 +2266,11 @@ impl ChatWidget {
         }
 
         if !text.is_empty() {
-            items.push(UserInput::Text { text: text.clone() });
+            // TODO: Thread text element ranges from the composer input. Empty keeps old behavior.
+            items.push(UserInput::Text {
+                text: text.clone(),
+                text_elements: Vec::new(),
+            });
         }
 
         if let Some(skills) = self.bottom_pane.skills() {