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/protocol.rs

@@ -372,10 +372,13 @@ impl ChatWidget {
         notification: ItemCompletedNotification,
         replay_kind: Option<ReplayKind>,
     ) {
-        self.handle_thread_item(
-            notification.item,
-            notification.turn_id,
-            replay_kind.map_or(ThreadItemRenderSource::Live, ThreadItemRenderSource::Replay),
-        );
+        match notification.item {
+            item @ ThreadItem::CommandExecution { .. } => self.on_command_execution_completed(item),
+            item => self.handle_thread_item(
+                item,
+                notification.turn_id,
+                replay_kind.map_or(ThreadItemRenderSource::Live, ThreadItemRenderSource::Replay),
+            ),
+        }
     }
 }