fix: 修复chatlog会话元数据回写与覆盖问题

- 为消息追加命令补充用户、助手与会话标题元信息

- 持久化后按会话聚合触发createOrTouch并优化空值覆盖策略

- 增加ChatPersistMySqlApplyService单测覆盖会话回写链路

easyflow-modules/easyflow-module-chatlog/src/test/java/tech/easyflow/chatlog/service/ChatPersistMySqlApplyServiceTest.java

@@ -0,0 +1,72 @@
+package tech.easyflow.chatlog.service;
+
+import org.junit.Assert;
+import org.junit.Test;
+import tech.easyflow.chatlog.domain.command.ChatAppendMessageCommand;
+import tech.easyflow.chatlog.domain.command.ChatSessionUpsertCommand;
+
+import java.math.BigInteger;
+import java.util.Date;
+import java.util.List;
+
+public class ChatPersistMySqlApplyServiceTest {
+
+    private final ChatPersistMySqlApplyService service =
+            new ChatPersistMySqlApplyService(null, null, null, null);
+
+    @Test
+    public void shouldBuildMissingSessionUpsertFromMessageMetadata() {
+        ChatAppendMessageCommand first = new ChatAppendMessageCommand();
+        first.setSessionId(BigInteger.valueOf(101));
+        first.setTenantId(BigInteger.ONE);
+        first.setDeptId(BigInteger.TEN);
+        first.setUserId(BigInteger.valueOf(12));
+        first.setUserAccount("admin");
+        first.setAssistantId(BigInteger.valueOf(99));
+        first.setAssistantCode("test-bot");
+        first.setAssistantName("测试助手");
+        first.setSessionTitle("你是谁");
+        first.setCreatedBy(BigInteger.valueOf(12));
+        first.setCreated(new Date(1_000L));
+
+        ChatAppendMessageCommand second = new ChatAppendMessageCommand();
+        second.setSessionId(BigInteger.valueOf(101));
+        second.setTenantId(BigInteger.ONE);
+        second.setDeptId(BigInteger.TEN);
+        second.setUserId(BigInteger.valueOf(12));
+        second.setAssistantId(BigInteger.valueOf(99));
+        second.setCreatedBy(BigInteger.valueOf(12));
+        second.setCreated(new Date(2_000L));
+
+        List<ChatSessionUpsertCommand> upserts = service.buildSessionUpserts(List.of(first, second));
+
+        Assert.assertEquals(1, upserts.size());
+        ChatSessionUpsertCommand upsert = upserts.get(0);
+        Assert.assertEquals(BigInteger.valueOf(101), upsert.getSessionId());
+        Assert.assertEquals("admin", upsert.getUserAccount());
+        Assert.assertEquals("test-bot", upsert.getAssistantCode());
+        Assert.assertEquals("测试助手", upsert.getAssistantName());
+        Assert.assertEquals("你是谁", upsert.getTitle());
+        Assert.assertEquals(new Date(2_000L), upsert.getOperateAt());
+    }
+
+    @Test
+    public void shouldFallbackTitleWhenMessageMetadataMissing() {
+        ChatAppendMessageCommand command = new ChatAppendMessageCommand();
+        command.setSessionId(BigInteger.valueOf(202));
+        command.setTenantId(BigInteger.ONE);
+        command.setDeptId(BigInteger.ONE);
+        command.setUserId(BigInteger.valueOf(7));
+        command.setAssistantId(BigInteger.valueOf(8));
+        command.setCreatedBy(BigInteger.valueOf(7));
+        command.setCreated(new Date(3_000L));
+
+        List<ChatSessionUpsertCommand> upserts = service.buildSessionUpserts(List.of(command));
+
+        Assert.assertEquals(1, upserts.size());
+        ChatSessionUpsertCommand upsert = upserts.get(0);
+        Assert.assertEquals("", upsert.getUserAccount());
+        Assert.assertEquals("会话-202", upsert.getTitle());
+        Assert.assertEquals(BigInteger.valueOf(7), upsert.getOperatorId());
+    }
+}