fix(dcl+centralui): MxGateway tag browse — lazy attributes, frame-size cap, wider scrollable picker

Expanding a Galaxy object in the tag picker hung on "loading…": the browse
reply inlined every child's full attribute set (~152 KB), exceeding Akka's
128 KB remote frame, and remoting silently discarded the oversized reply.

Browse path (DataConnectionLayer):
- RealMxGatewayClient: navigation now uses BrowseChildren(include_attributes=
  false) — child objects only — and an object's own attributes load lazily via
  DiscoverHierarchy(root, max_depth=0) when it's expanded. Payload drops from
  ~152 KB/level to a few KB. Seam contract unchanged.
- DataConnectionActor.CapBrowseChildren: protocol-agnostic byte-budget cap
  (~100 KB) on every BrowseNodeResult before it crosses the site→central
  frame, OR-ing the adapter's own Truncated flag. Byte budget, not a count —
  the only bound that holds regardless of NodeId/attribute-name length.
- RealOpcUaClient: requestedMaxReferencesPerNode 1000 → 500 to narrow the
  window before the byte budget applies.
- Graceful gRPC Unimplemented handling → NotSupportedException →
  BrowseFailureKind.NotBrowsable with an actionable message (older gateway
  builds lacking BrowseChildren).

Picker UI (CentralUI):
- NodeBrowserDialog: modal-lg → modal-xl; new scoped .razor.css caps the tree
  at 55vh with its own scrollbar so manual entry + Select/Cancel stay visible.
- Protocol-agnostic failure messages (was hardcoded "OPC UA …"); renamed the
  leftover opcua-browser-tree class to node-browser-tree.

Tests: new frame-budget cap test + NotSupported=>NotBrowsable mapping test;
DCL suite 88/88. Doc: Component-DataConnectionLayer.md records the lazy
attribute-light browse and the frame-size guard.

src/ZB.MOM.WW.ScadaBridge.DataConnectionLayer/Adapters/RealOpcUaClient.cs

@@ -353,11 +353,16 @@ public class RealOpcUaClient : IOpcUaClient
         // Variables (selectable), Methods (display-only).
         var nodeClassMask = (uint)(NodeClass.Object | NodeClass.Variable | NodeClass.Method);
 
+        // requestedMaxReferencesPerNode: cap the server's per-call references so a
+        // huge flat folder cannot return an unbounded set. 500 leaves headroom for
+        // the downstream frame-size budget (DataConnectionActor.CapBrowseChildren)
+        // even with long string NodeIds; a non-empty continuation point surfaces as
+        // Truncated, prompting manual entry rather than auto-paging.
         var (_, continuationPoint, references) = await session.BrowseAsync(
             null,
             null,
             nodeToBrowse,
-            1000u,
+            500u,
             BrowseDirection.Forward,
             ReferenceTypeIds.HierarchicalReferences,
             true,