Java client: port stream-alarms and acknowledge-alarm

Adds the session-less alarm CLI subcommands to the Java CLI. stream-alarms
attaches to the gateway's central alarm feed (--filter-prefix, --limit, --json
— NDJSON, one AlarmFeedMessage per line); acknowledge-alarm is a unary ack
(--reference required, --comment, --operator). streamAlarms joins
queryActiveAlarms on MxGatewayClient and uses a new
MxGatewayAlarmFeedSubscription cancellable handle. Batch dispatch re-enters the
picocli command line per stdin line, so registering the two new subcommands
suffices.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

clients/java/zb-mom-ww-mxgateway-client/src/main/java/com/zb/mom/ww/mxgateway/client/MxGatewayAlarmFeedSubscription.java

@@ -0,0 +1,67 @@
+package com.zb.mom.ww.mxgateway.client;
+
+import io.grpc.stub.ClientCallStreamObserver;
+import io.grpc.stub.ClientResponseObserver;
+import io.grpc.stub.StreamObserver;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicReference;
+import mxaccess_gateway.v1.MxaccessGateway.AlarmFeedMessage;
+import mxaccess_gateway.v1.MxaccessGateway.StreamAlarmsRequest;
+
+/**
+ * Cancellable handle returned by {@code streamAlarms}.
+ *
+ * <p>Wraps a caller-supplied {@link StreamObserver} and exposes a
+ * {@link #cancel()} entry point that aborts the underlying gRPC call. The
+ * subscription also implements {@link AutoCloseable} so it can participate in
+ * try-with-resources blocks.
+ */
+public final class MxGatewayAlarmFeedSubscription implements AutoCloseable {
+    private final AtomicReference<ClientCallStreamObserver<StreamAlarmsRequest>> requestStream = new AtomicReference<>();
+    private final AtomicBoolean cancelled = new AtomicBoolean();
+
+    ClientResponseObserver<StreamAlarmsRequest, AlarmFeedMessage> wrap(StreamObserver<AlarmFeedMessage> observer) {
+        return new ClientResponseObserver<>() {
+            @Override
+            public void beforeStart(ClientCallStreamObserver<StreamAlarmsRequest> stream) {
+                requestStream.set(stream);
+                if (cancelled.get()) {
+                    stream.cancel("client cancelled alarm feed", null);
+                }
+            }
+
+            @Override
+            public void onNext(AlarmFeedMessage value) {
+                observer.onNext(value);
+            }
+
+            @Override
+            public void onError(Throwable error) {
+                observer.onError(error);
+            }
+
+            @Override
+            public void onCompleted() {
+                observer.onCompleted();
+            }
+        };
+    }
+
+    /**
+     * Cancels the underlying gRPC call. Safe to invoke before the call has
+     * started; cancellation is recorded and applied as soon as the stream
+     * attaches.
+     */
+    public void cancel() {
+        cancelled.set(true);
+        ClientCallStreamObserver<StreamAlarmsRequest> stream = requestStream.get();
+        if (stream != null) {
+            stream.cancel("client cancelled alarm feed", null);
+        }
+    }
+
+    @Override
+    public void close() {
+        cancel();
+    }
+}

clients/java/zb-mom-ww-mxgateway-client/src/main/java/com/zb/mom/ww/mxgateway/client/MxGatewayClient.java

@@ -18,6 +18,7 @@ import mxaccess_gateway.v1.MxAccessGatewayGrpc;
 import mxaccess_gateway.v1.MxaccessGateway.AcknowledgeAlarmReply;
 import mxaccess_gateway.v1.MxaccessGateway.AcknowledgeAlarmRequest;
 import mxaccess_gateway.v1.MxaccessGateway.ActiveAlarmSnapshot;
+import mxaccess_gateway.v1.MxaccessGateway.AlarmFeedMessage;
 import mxaccess_gateway.v1.MxaccessGateway.CloseSessionReply;
 import mxaccess_gateway.v1.MxaccessGateway.CloseSessionRequest;
 import mxaccess_gateway.v1.MxaccessGateway.MxCommandReply;
@@ -27,6 +28,7 @@ import mxaccess_gateway.v1.MxaccessGateway.OpenSessionReply;
 import mxaccess_gateway.v1.MxaccessGateway.OpenSessionRequest;
 import mxaccess_gateway.v1.MxaccessGateway.ProtocolStatusCode;
 import mxaccess_gateway.v1.MxaccessGateway.QueryActiveAlarmsRequest;
+import mxaccess_gateway.v1.MxaccessGateway.StreamAlarmsRequest;
 import mxaccess_gateway.v1.MxaccessGateway.StreamEventsRequest;
 
 /**
@@ -320,6 +322,27 @@ public final class MxGatewayClient implements AutoCloseable {
         return subscription;
     }
 
+    /**
+     * Attaches to the gateway's central alarm feed. The stream opens with one
+     * {@code AlarmFeedMessage} per currently-active alarm (the ConditionRefresh
+     * snapshot), then a single {@code snapshot_complete}, then a
+     * {@code transition} for every subsequent raise / acknowledge / clear.
+     *
+     * <p>Served by the gateway's always-on alarm monitor — no worker session is
+     * opened — so any number of clients may attach.
+     *
+     * @param request the {@code StreamAlarmsRequest}, optionally scoped by
+     *                alarm-reference prefix
+     * @param observer caller-supplied observer that receives feed messages and completion
+     * @return a cancellable subscription handle
+     */
+    public MxGatewayAlarmFeedSubscription streamAlarms(
+            StreamAlarmsRequest request, StreamObserver<AlarmFeedMessage> observer) {
+        MxGatewayAlarmFeedSubscription subscription = new MxGatewayAlarmFeedSubscription();
+        withStreamDeadline(rawAsyncStub()).streamAlarms(request, subscription.wrap(observer));
+        return subscription;
+    }
+
     @Override
     public void close() {
         if (ownedChannel != null) {