test(google): disarm genai client finalizers in realtime tests

[rkfshakti]

Fixes #6881

Problem

tests/test_plugin_openai_stt_context.py::test_use_realtime_defaults_to_the_only_transport_a_model_has[gpt-realtime-whisper-True] intermittently fails with:

Failed: Test leaked tasks:
Coroutine : BaseApiClient.aclose    google/genai/_api_client.py:2213
Coroutine : AsyncClient.aclose      google/genai/client.py:152

That test is synchronous and never touches google. The tasks come from tests/test_plugin_google_realtime.py — the only module in the unit suite that constructs genai clients.

Root cause

AsyncClient.__del__ and BaseApiClient.__del__ both do this unconditionally, with no check for a client that was already closed:

def __del__(self) -> None:
    try:
      asyncio.get_running_loop().create_task(self.aclose())
    except Exception:
      pass

RealtimeSession.aclose() closes client.aio, but that does not disarm the finalizer — the object stays garbage until the collector reaches it, which can be several modules later. fail_on_leaked_tasks diffs asyncio.all_tasks() around each test, so the task is charged to whatever test happens to be running then.

Fix

Disarm both finalizers at module import in tests/test_plugin_google_realtime.py — the only module that constructs genai clients. Sessions already close their clients explicitly, so the finalizers are pure redundancy.

Verified:

• Without the disarm, dropping a client schedules 2 pending AsyncClient.aclose tasks on the running loop
• With the disarm, zero tasks leak
• All 18 realtime tests pass; full unit suite passes (1735 passed)

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.