refactor: 简化 __getattr__ 和测试 helper (ce-simplify-code)

core/exceptions.py:
- __getattr__ 用循环 + getattr 替代三处显式列举异常名
- 异常名只在 _LLM_EXCEPTION_NAMES 中定义一次，新增异常只改元组

test_memory_models.py:
- 提取 _assert_uuid_default/_assert_utc_default/_assert_unique_ids helper
- 消除 TestEpisodeModel 与 TestExperienceModel 间 3 个方法的复制粘贴

行为保持不变：52 tests passed，ruff clean，import 兼容性验证通过。

src/agentkit/core/exceptions.py

@@ -146,15 +146,10 @@ _LLM_EXCEPTION_NAMES = ("LLMError", "LLMProviderError", "ModelNotFoundError")
 
 def __getattr__(name: str):  # PEP 562
     if name in _LLM_EXCEPTION_NAMES:
-        from agentkit.llm.exceptions import (  # noqa: PLC0415
-            LLMError,
-            LLMProviderError,
-            ModelNotFoundError,
-        )
+        import agentkit.llm.exceptions as _llm_exc  # noqa: PLC0415
 
-        globals()["LLMError"] = LLMError
-        globals()["LLMProviderError"] = LLMProviderError
-        globals()["ModelNotFoundError"] = ModelNotFoundError
+        for n in _LLM_EXCEPTION_NAMES:
+            globals()[n] = getattr(_llm_exc, n)
         return globals()[name]
     raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
 

tests/unit/test_memory_models.py

@@ -23,6 +23,26 @@ from sqlalchemy.dialects.postgresql import JSONB
 from agentkit.memory.models import EpisodeModel, ExperienceModel
 
 
+def _assert_uuid_default(id_default) -> None:
+    """SQLAlchemy wraps Python-side default callables to receive an execution
+    context; pass None for callables that don't inspect it."""
+    val = id_default(None)
+    assert isinstance(val, str)
+    uuid.UUID(val)  # raises ValueError if not a valid uuid4 string
+
+
+def _assert_utc_default(ts_default) -> None:
+    ts = ts_default(None)
+    assert isinstance(ts, datetime)
+    assert ts.tzinfo is not None
+    assert ts.utcoffset() == timezone.utc.utcoffset(None)
+
+
+def _assert_unique_ids(id_default, n: int = 100) -> None:
+    ids = {id_default(None) for _ in range(n)}
+    assert len(ids) == n
+
+
 class TestEpisodeModel:
     def test_tablename(self):
         assert EpisodeModel.__tablename__ == "episodic_memories"
@@ -70,24 +90,13 @@ class TestEpisodeModel:
         assert cols.quality_score.default.arg == 0.5
 
     def test_callable_default_id_is_uuid_string(self):
-        # SQLAlchemy wraps Python-side default callables to receive an execution
-        # context; pass None for callables that don't inspect it.
-        id_default = EpisodeModel.__table__.c.id.default.arg
-        val = id_default(None)
-        assert isinstance(val, str)
-        uuid.UUID(val)  # raises ValueError if not a valid uuid4 string
+        _assert_uuid_default(EpisodeModel.__table__.c.id.default.arg)
 
     def test_callable_default_created_at_is_utc(self):
-        ts_default = EpisodeModel.__table__.c.created_at.default.arg
-        ts = ts_default(None)
-        assert isinstance(ts, datetime)
-        assert ts.tzinfo is not None
-        assert ts.utcoffset() == timezone.utc.utcoffset(None)
+        _assert_utc_default(EpisodeModel.__table__.c.created_at.default.arg)
 
     def test_default_id_is_unique_across_calls(self):
-        id_default = EpisodeModel.__table__.c.id.default.arg
-        ids = {id_default(None) for _ in range(100)}
-        assert len(ids) == 100
+        _assert_unique_ids(EpisodeModel.__table__.c.id.default.arg)
 
     def test_construct_with_explicit_values(self):
         ts = datetime(2025, 1, 2, 3, 4, 5, tzinfo=timezone.utc)
@@ -202,22 +211,13 @@ class TestExperienceModel:
         assert cols.optimization_tips.default.arg(None) == []
 
     def test_callable_default_id_is_uuid_string(self):
-        id_default = ExperienceModel.__table__.c.id.default.arg
-        val = id_default(None)
-        assert isinstance(val, str)
-        uuid.UUID(val)
+        _assert_uuid_default(ExperienceModel.__table__.c.id.default.arg)
 
     def test_callable_default_created_at_is_utc(self):
-        ts_default = ExperienceModel.__table__.c.created_at.default.arg
-        ts = ts_default(None)
-        assert isinstance(ts, datetime)
-        assert ts.tzinfo is not None
-        assert ts.utcoffset() == timezone.utc.utcoffset(None)
+        _assert_utc_default(ExperienceModel.__table__.c.created_at.default.arg)
 
     def test_default_id_is_unique_across_calls(self):
-        id_default = ExperienceModel.__table__.c.id.default.arg
-        ids = {id_default(None) for _ in range(100)}
-        assert len(ids) == 100
+        _assert_unique_ids(ExperienceModel.__table__.c.id.default.arg)
 
     def test_construct_with_explicit_values(self):
         ts = datetime(2025, 6, 7, 8, 9, 10, tzinfo=timezone.utc)