PR 6.3 — Buffered update interval landing

Wires MxAccess.PublishingIntervalMs into the gw's SubscribeBulk
bufferedUpdateIntervalMs parameter on both subscribe paths:

- GalaxyDriver.SubscribeAsync — when the caller passes TimeSpan.Zero
  (typical for infrastructure callers like the deploy watcher), the
  driver substitutes _options.MxAccess.PublishingIntervalMs. When the
  caller sets a non-zero interval (the server's UA subscription
  publishingInterval), that wins.
- PerPlatformProbeWatcher — new bufferedUpdateIntervalMs ctor parameter
  defaulting to 0 (gw default cadence). GalaxyDriver passes
  _options.MxAccess.PublishingIntervalMs so probe ScanState changes
  publish at the configured rate.

Tests: caller-wins-when-non-zero, fallback-to-config-when-zero on the
driver; default-zero, configured-forwarded, negative-rejected on the
probe watcher.

A session-level SetBufferedUpdateInterval RPC exists in the gw protocol
(MxCommandKind.SetBufferedUpdateInterval) but the .NET client doesn't
expose a typed helper yet — adjusting an existing subscription's
interval is a follow-up. Today's path subscribes once with the right
interval, which covers the common case.

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

src/ZB.MOM.WW.OtOpcUa.Driver.Galaxy/GalaxyDriver.cs

@@ -209,7 +209,9 @@ public sealed class GalaxyDriver
 
         _supervisor.StateChanged += OnSupervisorStateChanged;
 
-        _probeWatcher = new PerPlatformProbeWatcher(_subscriber, _hostStatuses, _logger);
+        _probeWatcher = new PerPlatformProbeWatcher(
+            _subscriber, _hostStatuses, _logger,
+            bufferedUpdateIntervalMs: _options.MxAccess.PublishingIntervalMs);
     }
 
     /// <summary>
@@ -441,7 +443,12 @@ public sealed class GalaxyDriver
             return new GalaxySubscriptionHandle(subscriptionId);
         }
 
-        var bufferedIntervalMs = (int)Math.Max(0, publishingInterval.TotalMilliseconds);
+        // PR 6.3 — when the caller doesn't set a publishing interval (TimeSpan.Zero or
+        // negative), fall back to the configured MxAccess.PublishingIntervalMs. The
+        // server's UA subscription publishingInterval drives this in production; tests
+        // and infrastructure callers (probe watcher, deploy watcher) hit the fallback.
+        var requested = (int)Math.Max(0, publishingInterval.TotalMilliseconds);
+        var bufferedIntervalMs = requested > 0 ? requested : _options.MxAccess.PublishingIntervalMs;
         var results = await _subscriber
             .SubscribeBulkAsync(fullReferences, bufferedIntervalMs, cancellationToken)
             .ConfigureAwait(false);