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/tests/common/test_codex.rs

@@ -270,6 +270,7 @@ impl TestCodex {
             .submit(Op::UserTurn {
                 items: vec![UserInput::Text {
                     text: prompt.into(),
+                    text_elements: Vec::new(),
                 }],
                 final_output_json_schema: None,
                 cwd: self.cwd.path().to_path_buf(),