Go client: port stream-alarms and acknowledge-alarm

Adds the session-less alarm CLI subcommands to mxgw-go. 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 the
public Client and is wired through the existing batch dispatcher via runWithIO.
SDK type aliases for StreamAlarmsRequest / AlarmFeedMessage / StreamAlarmsClient
land alongside the existing alarm types.

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

clients/go/mxgateway/galaxy_test.go

@@ -55,8 +55,8 @@ func TestGalaxyGetLastDeployTimeReturnsTimestampWhenPresent(t *testing.T) {
 	want := time.Date(2026, 4, 28, 12, 34, 56, 0, time.UTC)
 	fake := &fakeGalaxyServer{
 		deployReply: &pb.GetLastDeployTimeReply{
-			Present:           true,
-			TimeOfLastDeploy:  timestamppb.New(want),
+			Present:          true,
+			TimeOfLastDeploy: timestamppb.New(want),
 		},
 	}
 	client, cleanup := newGalaxyBufconnClient(t, fake)