fix(localdb): fault live sync session on cap-prune; keepalive + newest-wins sync guard (0.3.2, ScadaBridge arch-review P4-1 + P4-3)

ZB.MOM.WW.LocalDb/tests/ZB.MOM.WW.LocalDb.Tests/GrpcAdapterTests.cs

@@ -70,8 +70,12 @@ public sealed class GrpcAdapterTests : IAsyncLifetime
     }
 
     [Fact]
-    public async Task SecondConcurrentStream_Rejected()
+    public async Task SecondConcurrentStream_DisplacesTheIncumbent()
     {
+        // Newest wins (0.3.2). The guard serializes sessions; it was never a fence — the auth
+        // interceptor is, and an authenticated same-key dialler IS the peer. Refusing the newcomer
+        // bought nothing and cost the pair its only route back from a half-open link, where the
+        // incumbent handler can hold the guard indefinitely on a dead stream.
         var serverHost = await BuildServerAsync(NewDbPath(), apiKey: null, sink: null);
         var serverDb = serverHost.Services.GetRequiredService<ILocalDb>();
         var handler = serverHost.GetTestServer().CreateHandler();
@@ -85,11 +89,15 @@ public sealed class GrpcAdapterTests : IAsyncLifetime
 
         // Convergence proves the first stream's server handler is active and holding the single-stream guard.
         await WaitForAsync(async () => (await ReadOrders(serverDb)).Count == 1, RunTimeout);
+        var attemptsBefore = bg.ConnectionAttempts;
 
         var client = new LocalDbSync.LocalDbSyncClient(ChannelOver(handler));
         using var call2 = client.Sync(cancellationToken: cts.Token);
-        var ex = await Assert.ThrowsAsync<RpcException>(() => call2.ResponseStream.MoveNext(cts.Token));
-        Assert.Equal(StatusCode.AlreadyExists, ex.StatusCode);
+        Assert.True(await call2.ResponseStream.MoveNext(cts.Token));
+        Assert.Equal(SyncMessage.MsgOneofCase.Handshake, call2.ResponseStream.Current.MsgCase);
+
+        // The incumbent really ended: the displaced client notices and dials again.
+        await WaitForAsync(() => Task.FromResult(bg.ConnectionAttempts > attemptsBefore), RunTimeout);
 
         await bg.StopAsync(CancellationToken.None);
     }
@@ -262,9 +270,13 @@ public sealed class GrpcAdapterTests : IAsyncLifetime
             TombstoneRetention = TimeSpan.Zero,
             ReconnectBackoffMax = TimeSpan.Zero,
             MaxHlcDriftAhead = TimeSpan.Zero,
+            KeepAlivePingDelay = TimeSpan.Zero,
+            KeepAlivePingTimeout = TimeSpan.Zero,
         });
 
         Assert.True(result.Failed);
+        Assert.Contains(result.Failures, f => f.Contains("KeepAlivePingDelay", StringComparison.Ordinal));
+        Assert.Contains(result.Failures, f => f.Contains("KeepAlivePingTimeout", StringComparison.Ordinal));
         Assert.Contains(result.Failures, f => f.Contains("FlushInterval", StringComparison.Ordinal));
         Assert.Contains(result.Failures, f => f.Contains("MaxBatchSize", StringComparison.Ordinal));
         Assert.Contains(result.Failures, f => f.Contains("MaxOplogRows", StringComparison.Ordinal));