Redesign integration test architecture to eliminate async/sync deadlock:
- Run SimulationServer in dedicated background thread with own event loop
- Rewrite TempCo tests as fully synchronous (no @pytest.mark.asyncio)
- Add ServerThread fixture in tests/integration/conftest.py
- Fix Unicode encoding errors (replace deg, mu, +/- with ASCII)
- Optimize temperature points for faster settling (23C, 25C, 27C)
All 3 TempCo integration tests now passing in ~5 minutes total.
Move synchronous test execution to thread pool executor to avoid
blocking the async event loop. This prevents deadlocks when sync
client code tries to communicate with async server in same loop.
Note: Integration tests still experiencing timeouts - needs further
investigation. Unit tests and TCP server communication are working.
