approval ui (#1933)

Asking for approval:

<img width="269" height="41" alt="image"
src="https://github.com/user-attachments/assets/b9ced569-3297-4dae-9ce7-0b015c9e14ea"
/>

Allow:

<img width="400" height="31" alt="image"
src="https://github.com/user-attachments/assets/92056b22-efda-4d49-854d-e2943d5fcf17"
/>

Reject:

<img width="372" height="30" alt="image"
src="https://github.com/user-attachments/assets/be9530a9-7d41-4800-bb42-abb9a24fc3ea"
/>

Always Approve:

<img width="410" height="36" alt="image"
src="https://github.com/user-attachments/assets/acf871ba-4c26-4501-b303-7956d0151754"
/>

codex-rs/tui/src/history_cell.rs

@@ -435,7 +435,8 @@ impl HistoryCell {
             view: TextBlock::new(lines),
         }
     }
-
+    // allow dead code for now. maybe we'll use it again.
+    #[allow(dead_code)]
     pub(crate) fn new_background_event(message: String) -> Self {
         let mut lines: Vec<Line<'static>> = Vec::new();
         lines.push(Line::from("event".dim()));