Home Assistant's shared session defaults to ClientTimeout(total=300),
which cut a healthy event stream every five minutes; transitions fired
during the reconnect window are not replayed. The stream request now
passes ClientTimeout(total=None, sock_connect=<client timeout>), with
aiohttp imported lazily so the client stays importable without it.
Tests run the stream path against a stand-in aiohttp module fixture.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>