Fix 4 failing CI integration tests: empty broker list crash, TOPIC_NOT_EXIST consumer deadlock, test ordering race

[Copilot]

Three distinct bugs caused 4 CI integration tests to fail against RocketMQ 5.3.1 with auto-topic-creation enabled.

Fix 1 — MqBase.cs: crash on empty broker list (RequestSyncTest)

.First() on a LINQ sequence throws InvalidOperationException when RocketMQ returns no writable brokers for a brand-new topic.

// Before — throws if no writable broker exists
var writeQueueNums = rs.Where(...).Select(e => e.WriteQueueNums).First();

// After — safe default
var writeQueueNums = rs.Where(...).Select(e => e.WriteQueueNums).FirstOrDefault();
if (writeQueueNums > 0)
    DefaultTopicQueueNums = Math.Min(DefaultTopicQueueNums, writeQueueNums);

Fix 2 — Consumer.cs: consumer permanently stuck on new topic (MultiTopic, ProducerTracerTests)

InitOffsetAsync called UpdateOffset() which throws ResponseException(TOPIC_NOT_EXIST) for topics not yet registered on the broker. The exception escaped Rebalance() after _Queues was already assigned but before return true, so DoSchedule() was never called — the consumer deadlocked with no pull threads, and all subsequent rebalance checks found _Queues unchanged and short-circuited.

Two sub-fixes:

• QueryMaxOffset/QueryMinOffset return -1 for unknown topics (via ignoreError=true); clamp to 0 to start from the beginning rather than storing a sentinel.
• Catch ResponseException(TOPIC_NOT_EXIST) from UpdateOffset so the rebalance can complete; the offset is committed after the first successful consumption.

Fix 3 — ConsumerRetryDLQIntegrationTests.cs: message published before consumer ready (ConsumerRetry_DisabledRetry)

With FromLastOffset=true, publishing before the consumer starts means the consumer begins at MaxOffset=1, permanently skipping the message at offset 0. Reordered to: start consumer → wait for rebalance → start producer and publish.

[Copilot]

Pull request overview

该 PR 针对 RocketMQ 5.3.1（开启自动建 Topic）场景下的 4 个 CI 集成测试失败问题，分别从 Broker 路由初始化健壮性、消费者初始偏移量初始化对“Topic 尚未创建”的容错，以及测试用例启动顺序/竞态三方面进行修复，从而避免崩溃、死锁与消息被永久跳过。

Changes:

• MqBase.OnStart()：当名称服务器返回“无可写 Broker”时不再因 First() 抛 InvalidOperationException 崩溃。
• Consumer.InitOffsetAsync()：对 QueryMaxOffset/QueryMinOffset 返回 -1（Topic 未创建）进行归零处理，并捕获 UpdateOffset 的 TOPIC_NOT_EXIST 使 Rebalance 能继续完成。
• ConsumerRetry_DisabledRetry 集成测试：调整为“先启动消费者并等待 Rebalance → 再发送消息”，避免 FromLastOffset=true 下的竞态导致跳过消息。

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
XUnitTestRocketMQ/Consumers/ConsumerRetryDLQIntegrationTests.cs	调整测试启动顺序，确保消费者就绪后再发消息，避免偏移量竞态导致用例不稳定。
NewLife.RocketMQ/MqBase.cs	获取路由信息时对“空可写 Broker 列表”做保护，避免启动期崩溃。
NewLife.RocketMQ/Consumer.cs	初始 offset 初始化对 Topic 未创建场景增加容错，避免 Rebalance 中断导致消费线程不启动。