test(harness): widen the deploy-seal timeout to match a real two-node deploy

Comparing full-suite runs on this branch against master in a clean worktree:
both fail 11 tests, 9 identical. Master's two extras are load-flaky unit tests
(AbCip Probe_loops, Galaxy EventPumpBoundedChannel); this branch's two extras
were both Host.IntegrationTests deploy-path tests — the area this change
re-times — so they are attributable here rather than to background flakiness.

Cause is margin, not correctness. These waits used to observe a coordinator
that sealed instantly on an empty expected-ack set; they now observe a real
ApplyAck round-trip from every configured node. 15s was enormous margin against
"instant" and thin against the real thing, so they failed only under full-suite
CPU contention.

Hoisted to TwoNodeClusterHarness.DeploySealTimeout (45s) so the reason is
recorded once rather than as four unexplained numbers.

DriverReconnectE2eTests is deliberately left alone: it seeds both ClusterNode
rows itself and unconditionally, so its expected-ack set is identical before and
after this change. Widening its timeout would be papering over a flake this
change did not cause.

Host.IntegrationTests 195/201; sole failure AbCip_Green_AgainstSim, verified
failing on master.

Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW

tests/Server/ZB.MOM.WW.OtOpcUa.Host.IntegrationTests/TwoNodeClusterHarness.cs

@@ -96,6 +96,16 @@ public sealed class TwoNodeClusterHarness : IAsyncDisposable
     // host:port into NodeId so the cluster membership stays distinct on different ports.
     public const string LoopbackHost = "127.0.0.1";
 
+    /// <summary>
+    ///     How long a deploy-seal assertion waits. Generous on purpose: since per-cluster mesh
+    ///     Phase 1 the coordinator waits for a real ApplyAck from every configured node before
+    ///     sealing, so this measures an end-to-end two-node deploy rather than — as it did when the
+    ///     expected-ack set came up empty — an immediate seal. The old 15s had enormous margin
+    ///     against "instant" and thin margin against the real thing, which showed up as deploy
+    ///     tests failing only under full-suite CPU contention.
+    /// </summary>
+    public static readonly TimeSpan DeploySealTimeout = TimeSpan.FromSeconds(45);
+
     /// <summary>Gets the Akka ActorSystem for node A.</summary>
     public ActorSystem NodeASystem => NodeA.Services.GetRequiredService<ActorSystem>();
     /// <summary>Gets the Akka ActorSystem for node B.</summary>