burst paste edge cases (#2683)

This PR fixes two edge cases in managing burst paste (mainly on power
shell).
Bugs:
- Needs an event key after paste to render the pasted items

> ChatComposer::flush_paste_burst_if_due() flushes on timeout. Called:
>     - Pre-render in App on TuiEvent::Draw.
>     - Via a delayed frame
>
BottomPane::request_redraw_in(ChatComposer::recommended_paste_flush_delay()).

- Parses two key events separately before starting parsing burst paste

> When threshold is crossed, pull preceding burst chars out of the
textarea and prepend to paste_burst_buffer, then keep buffering.

- Integrates with #2567 to bring image pasting to windows.

codex-rs/tui/src/chatwidget.rs

@@ -604,6 +604,7 @@ impl ChatWidget {
                 has_input_focus: true,
                 enhanced_keys_supported,
                 placeholder_text: placeholder,
+                disable_paste_burst: config.disable_paste_burst,
             }),
             active_exec_cell: None,
             config: config.clone(),
@@ -652,6 +653,7 @@ impl ChatWidget {
                 has_input_focus: true,
                 enhanced_keys_supported,
                 placeholder_text: placeholder,
+                disable_paste_burst: config.disable_paste_burst,
             }),
             active_exec_cell: None,
             config: config.clone(),
@@ -858,6 +860,24 @@ impl ChatWidget {
         self.bottom_pane.handle_paste(text);
     }
 
+    // Returns true if caller should skip rendering this frame (a future frame is scheduled).
+    pub(crate) fn handle_paste_burst_tick(&mut self, frame_requester: FrameRequester) -> bool {
+        if self.bottom_pane.flush_paste_burst_if_due() {
+            // A paste just flushed; request an immediate redraw and skip this frame.
+            self.request_redraw();
+            true
+        } else if self.bottom_pane.is_in_paste_burst() {
+            // While capturing a burst, schedule a follow-up tick and skip this frame
+            // to avoid redundant renders between ticks.
+            frame_requester.schedule_frame_in(
+                crate::bottom_pane::ChatComposer::recommended_paste_flush_delay(),
+            );
+            true
+        } else {
+            false
+        }
+    }
+
     fn flush_active_exec_cell(&mut self) {
         if let Some(active) = self.active_exec_cell.take() {
             self.last_history_was_exec = true;