fix: esc w/ queued messages overwrites draft in composer (#4237)

Instead of overwriting the contents of the composer when pressing
<kbd>Esc</kbd> when there's a queued message, prepend the queued
message(s) to the composer draft.

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

@@ -264,7 +264,6 @@ impl ChatComposer {
     }
 
     /// Get the current composer text.
-    #[cfg(test)]
     pub(crate) fn current_text(&self) -> String {
         self.textarea.text().to_string()
     }

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

@@ -262,7 +262,6 @@ impl BottomPane {
     }
 
     /// Get the current composer text (for tests and programmatic checks).
-    #[cfg(test)]
     pub(crate) fn composer_text(&self) -> String {
         self.composer.current_text()
     }