Track TUI command completion separately from output (#34218)

## Why

App-server command output deltas populate an exec cell before the command
finishes. Treating the presence of output as completion can therefore mark a
streaming command inactive too early and mishandle it when the turn is
interrupted.

## What changed

- Use the recorded duration, which is set when a command ends, as the exec
  call's completion marker.
- Preserve streamed output when marking unfinished calls as failed and render
  status lines only after completion.
- Keep a single aggregated output representation and render truncated output
  without collecting every line first.
- Append grouped exploration calls in place and coalesce adjacent reads while
  rendering without cloning the calls.

## Testing

- Add snapshots covering active streamed output, transcript output, and the
  resulting history entry after interruption.
- Add coverage for truncating newline-dense output.

GitOrigin-RevId: 420ac1e5fe1b9fcdbdaa5a8998f3e43a5b720254

codex-rs/tui/src/chatwidget/tests/app_server.rs

@@ -850,6 +850,57 @@ async fn live_app_server_command_execution_strips_shell_wrapper() {
     );
 }
 
+#[tokio::test]
+async fn live_app_server_command_output_delta_transcript_snapshot() {
+    let (mut chat, mut rx, _op_rx) = make_chatwidget_manual(/*model_override*/ None).await;
+    chat.on_task_started();
+    begin_exec(&mut chat, "cmd-1", "printf 'stdout\\nstderr\\n'");
+
+    for delta in ["stdout\n", "stderr\n"] {
+        chat.handle_server_notification(
+            ServerNotification::CommandExecutionOutputDelta(
+                codex_app_server_protocol::CommandExecutionOutputDeltaNotification {
+                    thread_id: "thread-1".to_string(),
+                    turn_id: "turn-1".to_string(),
+                    item_id: "cmd-1".to_string(),
+                    delta: delta.to_string(),
+                },
+            ),
+            /*replay_kind*/ None,
+        );
+    }
+
+    let active = active_blob(&chat);
+    assert_chatwidget_snapshot!("live_app_server_command_output_delta_active", active);
+
+    let transcript = chat
+        .active_cell_transcript_lines(/*width*/ 80)
+        .expect("active exec transcript lines");
+    assert_chatwidget_snapshot!(
+        "live_app_server_command_output_delta_transcript",
+        lines_to_single_string(&transcript)
+    );
+
+    handle_turn_interrupted(&mut chat, "turn-1");
+    let mut completed = None;
+    while let Ok(event) = rx.try_recv() {
+        if let AppEvent::InsertHistoryCell(cell) = event {
+            let transcript = lines_to_single_string(&cell.transcript_lines(/*width*/ 80));
+            if transcript.contains("printf 'stdout\\nstderr\\n'") {
+                completed = Some(transcript);
+            }
+        }
+    }
+    let completed = completed.expect("expected the interrupted command in history");
+    let completed = regex_lite::Regex::new(r"(?m) • (?:\d+ms|\d+\.\d+s|\d+m \d+s)$")
+        .expect("valid duration regex")
+        .replace(&completed, " • <duration>");
+    assert_chatwidget_snapshot!(
+        "live_app_server_command_output_delta_interrupted",
+        completed
+    );
+}
+
 #[tokio::test]
 async fn live_app_server_collab_wait_items_render_history() {
     let (mut chat, mut rx, _op_rx) = make_chatwidget_manual(/*model_override*/ None).await;