* fix: run bcrypt off the event loop in auth routes
The auth routes are async, but each bcrypt call ran synchronously on the event
loop. bcrypt (checkpw/hashpw) is intentionally CPU-expensive (~100-300 ms), so
every login / signup / setup / change-password froze the single event loop for
that window, stalling all other in-flight requests (chat streams, polling, ...).
/api/auth/login is the worst case: it is reachable unauthenticated, runs bcrypt
twice (verify_password, then create_session re-verifies), and is rate-limited
only per-IP. A burst of login attempts serializes the whole server — cheap
DoS amplification.
Offload the bcrypt-bearing AuthManager calls (setup, signup/create_user,
login's verify_password + create_session, change_password) via
asyncio.to_thread, matching how the codebase already offloads blocking work
(e.g. src/builtin_actions._run_subprocess, email summarize). The event loop
stays responsive while bcrypt runs on a worker thread.
Add tests/test_auth_event_loop.py: asserts login runs verify_password and
create_session on a worker thread, not the loop thread. Fails if those calls
are awaited inline again.
* test: isolate auth event-loop test from heavy core/* import chain
The regression test imported routes.auth_routes, which pulls in
core.auth and so triggers core/__init__.py — transitively importing
src.llm_core (hangs at import under the project venv) and the SQLAlchemy
declarative models (metaclass error on a bare core.database import / under
the conftest sqlalchemy stubs). Reported by the maintainer: collection
failed on system Python and hung under the venv.
Stub core.auth/core.database before the import, mirroring the existing
_ensure_stub pattern in test_auth_regressions.py and test_null_owner_gates.py.
AuthManager is only a type hint here and the handler is exercised with a
MagicMock, so no real core machinery is needed. Test now imports cleanly
and passes in <0.3s without bcrypt/sqlalchemy installed.
