Compact successful command activity in the TUI (#38921)

## What changed

- Group consecutive successful agent and unified-exec startup commands into a compact `Ran N commands` entry while preserving their full transcript.
- Flush command groups at interaction boundaries, after failures, and after 32 completed commands. Keep manual shell commands and failed or declined commands visible.
- Apply the same grouping rules when replaying thread history without duplicating command starts or disturbing unrelated active commands.

## Testing

- Add TUI coverage for live and replayed grouping, transcript preservation, failures, overlapping commands, group limits, and interaction boundaries.

GitOrigin-RevId: d6602a20201644012fcff3d6cecf4690024383a9

codex-rs/tui/src/chatwidget.rs

@@ -1207,6 +1207,9 @@ impl ChatWidget {
     pub(crate) fn pre_draw_tick(&mut self) {
         self.update_due_hook_visibility();
         self.schedule_hook_timer_if_needed();
+        if self.bottom_pane.has_active_view() {
+            self.flush_completed_command_activity();
+        }
         self.bottom_pane.pre_draw_tick();
         if let Some(pet) = self.ambient_pet.as_ref() {
             pet.schedule_next_frame();
@@ -1233,6 +1236,18 @@ impl ChatWidget {
         }
     }
 
+    fn flush_completed_command_activity(&mut self) {
+        if self
+            .transcript
+            .active_cell
+            .as_ref()
+            .and_then(|cell| cell.as_any().downcast_ref::<ExecCell>())
+            .is_some_and(|cell| !cell.is_active())
+        {
+            self.flush_active_cell();
+        }
+    }
+
     pub(crate) fn add_to_history(&mut self, cell: impl HistoryCell + 'static) {
         self.add_boxed_history(Box::new(cell));
     }
@@ -1262,6 +1277,15 @@ impl ChatWidget {
                 self.flush_active_cell();
             }
             self.transcript.needs_final_message_separator = true;
+        } else if !keep_placeholder_header_active
+            && self
+                .transcript
+                .active_cell
+                .as_ref()
+                .is_some_and(|active_cell| active_cell.as_any().is::<ExecCell>())
+            && !cell.transcript_lines(history_width).is_empty()
+        {
+            self.flush_completed_command_activity();
         }
         self.app_event_tx.send(AppEvent::InsertHistoryCell(cell));
     }