Summary

• add a narrow TUI slash_worker orphan reaper for stale direct-child worker processes
• trigger throttled reaping on session create/close and force it during TUI gateway shutdown
• cover process-safety behavior with regression tests

Verification

• python -m pytest tests/test_tui_gateway_server.py -q
• python -m pytest tests/test_tui_gateway_server.py::test_session_create_close_race_does_not_orphan_worker tests/test_tui_gateway_server.py::test_session_create_no_race_keeps_worker_alive tests/test_tui_gateway_server.py::test_get_db_degrades_cleanly_when_sessiondb_init_fails tests/test_lazy_session_regressions.py -q
• python -m py_compile tui_gateway/server.py tests/test_tui_gateway_server.py
• static diff scan: no findings
• independent reviewer: passed