Document asyncio isolation in offer CLI test

Add a short comment explaining why the helper uses a private event loop instead of asyncio.run(): the latter clears the current loop on Python 3.9/3.10 and can break later tests in the same worker.

Author: Andrey Cheptsov

src/tests/_internal/cli/utils/test_offer.py

@@ -36,6 +36,8 @@ def _get_offer(index: int) -> InstanceOfferWithAvailability:
 
 def _get_run_plan(*, offers: list[InstanceOfferWithAvailability], total_offers: int) -> RunPlan:
     run_spec = get_run_spec(repo_id="test-repo")
+    # Keep this helper's asyncio state isolated. `asyncio.run()` clears the current event loop
+    # on Python 3.9/3.10, which can break later tests that still expect one to exist.
     loop = asyncio.new_event_loop()
     try:
         job = loop.run_until_complete(