custom textarea (#1794)

This replaces tui-textarea with a custom textarea component.

Key differences:
1. wrapped lines
2. better unicode handling
3. uses the native terminal cursor

This should perhaps be spun out into its own separate crate at some
point, but for now it's convenient to have it in-tree.

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

@@ -19,6 +19,7 @@ mod chat_composer_history;
 mod command_popup;
 mod file_search_popup;
 mod status_indicator_view;
+mod textarea;
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub(crate) enum CancellationEvent {
@@ -36,7 +37,7 @@ use status_indicator_view::StatusIndicatorView;
 pub(crate) struct BottomPane<'a> {
     /// Composer is retained even when a BottomPaneView is displayed so the
     /// input state is retained when the view is closed.
-    composer: ChatComposer<'a>,
+    composer: ChatComposer,
 
     /// If present, this is displayed instead of the `composer`.
     active_view: Option<Box<dyn BottomPaneView<'a> + 'a>>,
@@ -74,7 +75,19 @@ impl BottomPane<'_> {
         self.active_view
             .as_ref()
             .map(|v| v.desired_height(width))
-            .unwrap_or(self.composer.desired_height())
+            .unwrap_or(self.composer.desired_height(width))
+    }
+
+    pub fn cursor_pos(&self, area: Rect) -> Option<(u16, u16)> {
+        // Hide the cursor whenever an overlay view is active (e.g. the
+        // status indicator shown while a task is running, or approval modal).
+        // In these states the textarea is not interactable, so we should not
+        // show its caret.
+        if self.active_view.is_some() {
+            None
+        } else {
+            self.composer.cursor_pos(area)
+        }
     }
 
     /// Forward a key event to the active view or the composer.