feat: jc 引擎主线搬入 app/engine（315 测试基线全绿：320 去掉 admin 5 用例）

Co-Authored-By: Claude Code <noreply@anthropic.com>

tests/conftest.py

@@ -0,0 +1,120 @@
+import os
+import tempfile
+import asyncio
+
+import pytest
+from sqlalchemy.ext.asyncio import create_async_engine, async_sessionmaker
+from sqlalchemy.pool import NullPool
+
+from app.engine.models import Base
+
+# `chat_rest` is created in Task A4. Tolerate its absence so earlier tasks
+# (e.g. A0's /health smoke) can use the `client` fixture without it.
+# Import `app.main` FIRST so the natural main -> chat_rest load order resolves
+# (chat_rest does `from app.main import async_session`; if conftest imports
+# chat_rest before main is loaded, main's `from chat_rest import router` hits
+# a partially-initialized module -> circular ImportError).
+_HAS_CHAT_REST = False
+chat_rest_mod = None
+try:
+    import app.main  # noqa: F401
+    import app.engine.routes.chat_rest as chat_rest_mod
+    _HAS_CHAT_REST = True
+except ModuleNotFoundError:
+    pass
+
+
+async def _create_all(engine):
+    async with engine.begin() as conn:
+        await conn.run_sync(Base.metadata.create_all)
+
+
+@pytest.fixture(scope="session", autouse=True)
+def _dispose_main_engine():
+    """Dispose `app.main.engine` at session end.
+
+    Best-effort cleanup: explicitly disposing the app-level engine before
+    interpreter shutdown reduces (but does NOT eliminate) the noisy
+    `Windows fatal exception: access violation` traces that aiosqlite worker
+    threads emit when interrupted mid-cleanup at interpreter exit.
+
+    Reality check on Windows:
+    - All tests pass and pytest exits 0; the traces are written to stderr
+      AFTER the run completes and do not affect pass/fail or the exit code.
+    - They originate from aiosqlite background threads being torn down by the
+      interpreter and are harmless.
+    - They do not occur on Linux/CI.
+    """
+    yield
+    from app.main import engine as main_engine
+    try:
+        asyncio.run(main_engine.dispose())
+    except Exception:
+        pass
+
+
+@pytest.fixture
+def async_db():
+    """Fresh temp-file SQLite sessionmaker for direct async-DB tests
+    (e.g. testing ConversationManager without HTTP). Isolated per test.
+    """
+    fd, path = tempfile.mkstemp(suffix=".db")
+    os.close(fd)
+    engine = create_async_engine(
+        f"sqlite+aiosqlite:///{path}", poolclass=NullPool
+    )
+    asyncio.run(_create_all(engine))
+    sm = async_sessionmaker(engine, expire_on_commit=False)
+    yield sm
+    asyncio.run(engine.dispose())
+    try:
+        os.remove(path)
+    except PermissionError:
+        pass
+
+
+@pytest.fixture(autouse=True)
+def _reset_rate_limit():
+    """Reset the in-memory rate limiter before and after every test so that
+    module-global bucket state can never leak across tests."""
+    from app.engine.services.rate_limit import _reset_for_test
+    _reset_for_test()
+    yield
+    _reset_for_test()
+
+
+@pytest.fixture
+def client(monkeypatch):
+    """Temporary file-SQLite TestClient with `chat_rest.async_session` overridden.
+
+    Design notes:
+    - File DB (not :memory:) avoids the StaticPool cross-loop reuse pitfall.
+    - `NullPool` closes each connection when the session returns it, so no
+      aiosqlite worker thread outlives the event loop that created it.
+      Together with `_dispose_main_engine`, this REDUCES but does NOT
+      eliminate the harmless Windows access-violation stderr traces described
+      above; it has no effect on test correctness or on Linux/CI.
+    - Monkeypatching the module-level `async_session` binding in `chat_rest`
+      works because the route handlers resolve it as a module global at call.
+    """
+    from fastapi.testclient import TestClient
+    from app.main import app
+
+    fd, path = tempfile.mkstemp(suffix=".db")
+    os.close(fd)
+    engine = create_async_engine(
+        f"sqlite+aiosqlite:///{path}", poolclass=NullPool
+    )
+    asyncio.run(_create_all(engine))
+    sm = async_sessionmaker(engine, expire_on_commit=False)
+    if _HAS_CHAT_REST:
+        monkeypatch.setattr(chat_rest_mod, "async_session", sm)
+
+    with TestClient(app) as c:
+        yield c
+
+    asyncio.run(engine.dispose())
+    try:
+        os.remove(path)
+    except PermissionError:
+        pass