feat: 添加 NapCat 适配器的入站消息编解码功能，增强插件配置更新逻辑和数据库交互测试

pytests/common_test/test_expression_learner.py

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+"""测试表达方式学习器的数据库读取行为。"""
+
+from contextlib import contextmanager
+from typing import Generator
+
+import pytest
+from sqlalchemy.pool import StaticPool
+from sqlmodel import Session, SQLModel, create_engine
+
+from src.bw_learner.expression_learner import ExpressionLearner
+from src.common.database.database_model import Expression
+
+
+@pytest.fixture(name="expression_learner_engine")
+def expression_learner_engine_fixture() -> Generator:
+    """创建用于表达方式学习器测试的内存数据库引擎。
+
+    Yields:
+        Generator: 供测试使用的 SQLite 内存引擎。
+    """
+    engine = create_engine(
+        "sqlite://",
+        connect_args={"check_same_thread": False},
+        poolclass=StaticPool,
+    )
+    SQLModel.metadata.create_all(engine)
+    yield engine
+
+
+def test_find_similar_expression_uses_read_only_session_and_history_content(
+    monkeypatch: pytest.MonkeyPatch,
+    expression_learner_engine,
+) -> None:
+    """查找相似表达方式时，应能在离开会话后安全使用结果，并比较历史情景内容。"""
+    import src.bw_learner.expression_learner as expression_learner_module
+
+    with Session(expression_learner_engine) as session:
+        session.add(
+            Expression(
+                situation="发送汗滴表情",
+                style="发送💦表情符号",
+                content_list='["表达情绪高涨或生理反应"]',
+                count=1,
+                session_id="session-a",
+                checked=False,
+                rejected=False,
+            )
+        )
+        session.commit()
+
+    @contextmanager
+    def fake_get_db_session(auto_commit: bool = True) -> Generator[Session, None, None]:
+        """构造带自动提交语义的测试会话工厂。
+
+        Args:
+            auto_commit: 退出上下文时是否自动提交。
+
+        Yields:
+            Generator[Session, None, None]: SQLModel 会话对象。
+        """
+        session = Session(expression_learner_engine)
+        try:
+            yield session
+            if auto_commit:
+                session.commit()
+        except Exception:
+            session.rollback()
+            raise
+        finally:
+            session.close()
+
+    monkeypatch.setattr(expression_learner_module, "get_db_session", fake_get_db_session)
+
+    learner = ExpressionLearner(session_id="session-a")
+    result = learner._find_similar_expression("表达情绪高涨或生理反应")
+
+    assert result is not None
+    expression, similarity = result
+    assert expression.item_id is not None
+    assert expression.style == "发送💦表情符号"
+    assert similarity == pytest.approx(1.0)