Scrollable slash commands (#1830)

Scrollable slash commands. Part 1 of the multi PR.

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

@@ -19,6 +19,9 @@ mod chat_composer_history;
 mod command_popup;
 mod file_search_popup;
 mod live_ring_widget;
+mod popup_consts;
+mod scroll_state;
+mod selection_popup_common;
 mod status_indicator_view;
 mod textarea;