Summary

• add a test cleanup helper that stops TUI notification pollers before dropping sessions
• update fake-agent session tests to use the helper instead of directly popping sessions
• prevents orphan daemon pollers from consuming later process-completion events in CI

Test Plan

• uv run --extra dev ruff check tests/test_tui_gateway_server.py
• uv run --extra dev python -m pytest tests/test_tui_gateway_server.py -q
• uv run --extra dev python -m pytest tests/test_tui_gateway_server.py::test_init_session_fires_reset_hook tests/test_tui_gateway_server.py::test_session_create_no_race_keeps_worker_alive tests/test_tui_gateway_server.py::test_session_create_continues_when_state_db_is_unavailable tests/test_tui_gateway_server.py::test_notification_poller_delivers_completion -q
• uv run --extra all python scripts/run_tests_parallel.py --slice 1/6 (passed once; later rerun showed two unrelated/environmental failures: stale plugin discovery cache and a flaky MCP event bridge poll test)