A cleanup review found that adding prompt.submit to _LONG_HANDLERS made the RPC
pool own the full first-turn wait even though the handler itself already spawns
a turn thread. Keep prompt.submit inline and make it return immediately:
- look up the session without waiting
- kick the lazy agent build
- spawn a short waiter thread that blocks on agent_ready, then starts the
existing turn dispatcher
This keeps stdin dispatch responsive, avoids occupying a bounded pool worker for
a normal chat turn, and preserves the lazy-start hydration behavior.
Tests:
- python -m py_compile tui_gateway/server.py
- cd ui-tui && npm run type-check && npm run build
- scripts/run_tests.sh tests/tui_gateway/test_protocol.py::test_sess_found tests/tools/test_code_execution_modes.py tests/tools/test_code_execution.py
- cd ui-tui && npm test -- --run src/__tests__/useSessionLifecycle.test.ts src/__tests__/useConfigSync.test.ts
72a3af63d4