Custom prompt args (numeric) (#4470)

[Cherry picked from /pull/3565]

Adds $1, $2, $3, $ARGUMENTS param parsing for custom prompts.

codex-rs/tui/src/bottom_pane/mod.rs

@@ -26,6 +26,7 @@ pub mod custom_prompt_view;
 mod file_search_popup;
 mod footer;
 mod list_selection_view;
+mod prompt_args;
 pub(crate) use list_selection_view::SelectionViewParams;
 mod paste_burst;
 pub mod popup_consts;