feat(opcuaclient-browser): real AttributesAsync + certificate-auth browse (R06:O-5)

- AttributesAsync was a stub returning nothing; it now reads NodeClass /
  DisplayName / DataType / ValueRank / UserAccessLevel in one request and maps them
  through UpstreamAttributeMapping, the same mapping discovery registers with (moved
  into the shared .Session leaf; the driver forwards to it). Objects have no value
  attributes.
- Certificate auth was refused "in v1". The browse now builds its identity through
  OpcUaUserIdentityFactory (shared .Session leaf, the driver forwards to it),
  including the secret: resolution of Password / UserCertificatePassword through the
  host's ISecretResolver (optional ctor param, DI-injected). Fail-closed: a secret:
  ref with no store throws instead of being sent as the literal (the browse used to
  send a secret: Password verbatim). The identity is built before any network I/O.

Refs #743

Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Browser/OpcUaClientBrowseSession.cs

@@ -54,10 +54,64 @@ internal sealed class OpcUaClientBrowseSession : IBrowseSession
     }
 
     /// <inheritdoc />
-    public Task<IReadOnlyList<AttributeInfo>> AttributesAsync(string nodeId, CancellationToken cancellationToken)
+    // R06:O-5 — reads the node's NodeClass / DisplayName / DataType / ValueRank / UserAccessLevel in one request and
+    // maps them through the same UpstreamAttributeMapping the runtime driver's discovery registers with, so the
+    // side-panel shows what a browse-commit would author. An Object (folder) has no value attributes → empty.
+    // Throws ArgumentException when nodeId cannot be resolved against the live session's namespace table.
+    public async Task<IReadOnlyList<AttributeInfo>> AttributesAsync(string nodeId, CancellationToken cancellationToken)
     {
+        ObjectDisposedException.ThrowIf(_disposed, this);
+        if (!NamespaceMap.TryResolve(_session, nodeId, out var resolved))
+            throw new ArgumentException(
+                $"Cannot resolve NodeId '{nodeId}' against the live session.", nameof(nodeId));
+
+        uint[] attributeIds =
+        [
+            Attributes.NodeClass, Attributes.DisplayName, Attributes.DataType, Attributes.ValueRank,
+            Attributes.UserAccessLevel,
+        ];
+        var toRead = new ReadValueIdCollection(attributeIds.Length);
+        foreach (var id in attributeIds) toRead.Add(new ReadValueId { NodeId = resolved, AttributeId = id });
+
+        DataValueCollection values;
+        await _gate.WaitAsync(cancellationToken).ConfigureAwait(false);
+        try
+        {
+            var resp = await _session.ReadAsync(
+                requestHeader: null,
+                maxAge: 0,
+                timestampsToReturn: TimestampsToReturn.Neither,
+                nodesToRead: toRead,
+                ct: cancellationToken).ConfigureAwait(false);
+            values = resp?.Results ?? [];
+        }
+        finally
+        {
+            _gate.Release();
+        }
         LastUsedUtc = DateTime.UtcNow;
-        return Task.FromResult<IReadOnlyList<AttributeInfo>>(Array.Empty<AttributeInfo>());
+
+        DataValue? At(int i) => i < values.Count && StatusCode.IsGood(values[i].StatusCode)
+            ? values[i] : null;
+
+        var nodeClass = At(0)?.Value is int nc ? (NodeClass)nc : NodeClass.Unspecified;
+        if (nodeClass != NodeClass.Variable) return Array.Empty<AttributeInfo>();
+
+        var name = (At(1)?.Value as LocalizedText)?.Text ?? resolved.ToString() ?? nodeId;
+        var dataType = At(2)?.Value is NodeId dt
+            ? UpstreamAttributeMapping.MapDataType(dt)
+            : ZB.MOM.WW.OtOpcUa.Core.Abstractions.DriverDataType.String;
+        var valueRank = At(3)?.Value is int vr ? vr : ValueRanks.Scalar;
+        var access = At(4)?.Value is byte ab ? ab : (byte)0;
+
+        return
+        [
+            new AttributeInfo(
+                Name: name,
+                DriverDataType: dataType.ToString(),
+                IsArray: UpstreamAttributeMapping.IsArray(valueRank),
+                SecurityClass: UpstreamAttributeMapping.MapAccessLevel(access).ToString()),
+        ];
     }
 
     /// <summary>Issue a single-level Browse (plus continuation-point follow-ups) under the