fleet: require a minimum version of the peer at the handshake [CI]

MoShiro__MinAgentVersion makes the backend refuse agents below it at hello (fleet_version_required); fleet.min_server_version or MOSHIRO_MIN_SERVER_VERSION makes the agent drop a backend below it. Either side waits five seconds and shakes hands again, because the other one may be updating.

backend/fleet/tests/Fleet.Tests/NodeVersionsTests.cs

@@ -0,0 +1,21 @@
+using Fleet.Core;
+
+namespace Fleet.Tests;
+
+public sealed class NodeVersionsTests
+{
+    [Theory]
+    [InlineData("0.4.2-dev.73-5245f03", "0.4.2-dev.74", true)]
+    [InlineData("0.4.2-dev.73-5245f03", "0.4.2-dev.73-abcdef0", false)] // 哈希不参与比较
+    [InlineData("0.4.2-dev.100-aaaaaaa", "0.4.2-dev.99", false)] // 序号按数字比，不是按字符串
+    [InlineData("0.4.2-dev.999", "0.4.2", true)] // 正式版高于预发布版
+    [InlineData("0.4.2", "0.4.2-dev.5", false)]
+    [InlineData("0.4.1", "0.4.2-dev.1", true)]
+    [InlineData("v0.5.0", "0.4.9", false)]
+    [InlineData("0.4.2-dev.73-5245f03", "", false)] // 没有要求
+    [InlineData("", "0.4.2", false)] // 认不出来的版本号不拒绝
+    [InlineData("not-a-version", "0.4.2", false)]
+    [InlineData("0.4.2", "garbage", false)]
+    public void IsBelow_ComparesCoreThenReleaseThenTheDevCounter(string actual, string required, bool expected) =>
+        Assert.Equal(expected, NodeVersions.IsBelow(actual, required));
+}