refactor(inbound-api): use the shared ZB.MOM.WW.Health IActiveNodeGate (ScadaBridge#80)

The InboundAPI carried its own IActiveNodeGate (implemented by Host/Health/ActiveNodeGate)
whose rule already matched the shared Health 0.3.0 AkkaActiveNodeGate — both route to
ClusterActiveNode (oldest Up member). The private interface and implementation are deleted;
InboundAPI references ZB.MOM.WW.Health (0.3.0, already pinned) and InboundApiEndpointFilter,
AuditWriteMiddleware, InboundMethodWarmupService and FlowDebugRunner consume
ZB.MOM.WW.Health.IActiveNodeGate. The Central branch of Program.cs registers
AkkaActiveNodeGate (unscoped, like the active-node health check).

Warm-up behaviour is kept: the shared gate answers false while no ActorSystem resolves, while
this member is not Up, and on any cluster-init fault. It resolves the ActorSystem through the
existing DI singleton bridge (GetOrCreateActorSystem), the same path the health probes use.

Tests: CompositionRoot asserts the shared gate type (fails with the registration removed);
the evaluator wiring test now drives AkkaActiveNodeGate; new warm-up test (no ActorSystem ->
not active). Nothing was missing from the Health 0.3.0 package.

(ScadaBridge#80)

Claude-Session: https://claude.ai/code/session_01GT67AEHd2Acv1YPwGfXEoV

tests/ZB.MOM.WW.ScadaBridge.Host.Tests/CompositionRootTests.cs

@@ -332,7 +332,7 @@ public class CentralCompositionRootTests : IDisposable
 
     /// <summary>
     /// Regression test: the Central composition root MUST register a
-    /// concrete <see cref="IActiveNodeGate"/> implementation. Without it,
+    /// concrete <see cref="ZB.MOM.WW.Health.IActiveNodeGate"/> implementation. Without it,
     /// <see cref="InboundApiEndpointFilter"/> falls through to "allow" and a
     /// standby central node continues to serve the inbound API, racing the
     /// active node and executing scripts against stale singleton state. The
@@ -344,12 +344,17 @@ public class CentralCompositionRootTests : IDisposable
     /// indistinguishable from "missing" at runtime, which is the failure mode
     /// the finding describes.
     /// </summary>
+    /// <remarks>
+    /// Gitea #80: the gate is the shared <see cref="ZB.MOM.WW.Health.IActiveNodeGate"/> backed by
+    /// <see cref="ZB.MOM.WW.Health.Akka.AkkaActiveNodeGate"/> — the same ClusterActiveNode rule as
+    /// the /health/active probe — not a ScadaBridge-private seam.
+    /// </remarks>
     [Fact]
     public void Central_IActiveNodeGate_IsRegisteredAsActiveNodeGate()
     {
-        var gate = _factory.Services.GetService<IActiveNodeGate>();
+        var gate = _factory.Services.GetService<ZB.MOM.WW.Health.IActiveNodeGate>();
         Assert.NotNull(gate);
-        Assert.IsType<ActiveNodeGate>(gate);
+        Assert.IsType<ZB.MOM.WW.Health.Akka.AkkaActiveNodeGate>(gate);
     }
 
     // --- ScadaBridge#22 regression ---