Add paste summarization to Codex TUI (#1549)

## Summary
- introduce `Paste` event to avoid per-character paste handling
- collapse large pasted blocks to `[Pasted Content X lines]`
- store the real text so submission still includes it
- wire paste handling through `App`, `ChatWidget`, `BottomPane`, and
`ChatComposer`

## Testing
- `cargo test -p codex-tui`


------
https://chatgpt.com/codex/tasks/task_i_6871e24abf80832184d1f3ca0c61a5ee


https://github.com/user-attachments/assets/eda7412f-da30-4474-9f7c-96b49d48fbf8

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

@@ -82,6 +82,15 @@ impl BottomPane<'_> {
         }
     }
 
+    pub fn handle_paste(&mut self, pasted: String) {
+        if self.active_view.is_none() {
+            let needs_redraw = self.composer.handle_paste(pasted);
+            if needs_redraw {
+                self.request_redraw();
+            }
+        }
+    }
+
     /// Update the status indicator text (only when the `StatusIndicatorView` is
     /// active).
     pub(crate) fn update_status_text(&mut self, text: String) {