Add UI features, alarm ack, historian UTC fix, and Client.UI documentation

Major changes across the client stack:
- Settings persistence (connection, subscriptions, alarm source)
- Deferred OPC UA SDK init for instant startup
- Array/status code formatting, write value popup, alarm acknowledgment
- Severity-colored alarm rows, condition dedup on server side
- DateTimeRangePicker control with preset buttons and UTC text input
- Historian queries use wwTimezone=UTC and OPCQuality column
- Recursive subscribe from tree, multi-select remove
- Connection panel with expander, folder chooser for cert path
- Dynamic tab headers showing subscription/alarm counts
- Client.UI.md documentation with headless-rendered screenshots

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/ZB.MOM.WW.LmxOpcUa.Client.UI.Tests/Fakes/FakeOpcUaClientService.cs

@@ -14,6 +14,7 @@ public sealed class FakeOpcUaClientService : IOpcUaClientService
     public ConnectionInfo? ConnectResult { get; set; }
     public Exception? ConnectException { get; set; }
     public IReadOnlyList<BrowseResult> BrowseResults { get; set; } = [];
+    public Dictionary<string, IReadOnlyList<BrowseResult>> BrowseResultsByParent { get; set; } = new();
     public Exception? BrowseException { get; set; }
 
     public DataValue ReadResult { get; set; } =
@@ -100,6 +101,10 @@ public sealed class FakeOpcUaClientService : IOpcUaClientService
         BrowseCallCount++;
         LastBrowseParentNodeId = parentNodeId;
         if (BrowseException != null) throw BrowseException;
+
+        if (parentNodeId != null && BrowseResultsByParent.TryGetValue(parentNodeId.ToString(), out var perParent))
+            return Task.FromResult(perParent);
+
         return Task.FromResult(BrowseResults);
     }
 
@@ -136,6 +141,18 @@ public sealed class FakeOpcUaClientService : IOpcUaClientService
         return Task.CompletedTask;
     }
 
+    public StatusCode AcknowledgeResult { get; set; } = StatusCodes.Good;
+    public Exception? AcknowledgeException { get; set; }
+    public int AcknowledgeCallCount { get; private set; }
+
+    public Task<StatusCode> AcknowledgeAlarmAsync(string conditionNodeId, byte[] eventId, string comment,
+        CancellationToken ct = default)
+    {
+        AcknowledgeCallCount++;
+        if (AcknowledgeException != null) throw AcknowledgeException;
+        return Task.FromResult(AcknowledgeResult);
+    }
+
     public Task<IReadOnlyList<DataValue>> HistoryReadRawAsync(NodeId nodeId, DateTime startTime, DateTime endTime,
         int maxValues = 1000, CancellationToken ct = default)
     {