chore: import upstream snapshot with attribution

.github/scripts/run-asyncio-teardown-stability.sh

@@ -0,0 +1,20 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+repeat_count="${1:-5}"
+
+asyncio_progress_args=(
+  tests/test_asyncio_progress.py
+)
+
+run_step_execution_args=(
+  tests/test_run_step_execution.py
+  -k
+  "cancel or post_invoke"
+)
+
+for run in $(seq 1 "$repeat_count"); do
+  echo "Async teardown stability run ${run}/${repeat_count}"
+  uv run pytest -q "${asyncio_progress_args[@]}"
+  uv run pytest -q "${run_step_execution_args[@]}"
+done