feat(opcuaclient): subscription tuning, OperationLimits chunking, diagnostics counters, revocation options, DiscoveryUrl (#273 #275 #276 #277 #278)

Claude-Session: https://claude.ai/code/session_01Ef2ozxS7QPanGT8uoATbTe

src/Core/ZB.MOM.WW.OtOpcUa.Core.Abstractions/DriverHealth.cs

@@ -15,10 +15,16 @@ namespace ZB.MOM.WW.OtOpcUa.Core.Abstractions;
 ///     carry a non-null message. Callers must not key behaviour on the LastError-null ↔ Healthy
 ///     pairing.
 /// </param>
+/// <param name="Diagnostics">
+///     Optional driver-specific counters/gauges (name → value) for the diagnostics surface (#276).
+///     Null for every driver that publishes none. Deliberately NOT part of any health-change
+///     fingerprint: counters move on every poll, so keying a dedup on them would defeat it.
+/// </param>
 public sealed record DriverHealth(
     DriverState State,
     DateTime? LastSuccessfulRead,
-    string? LastError);
+    string? LastError,
+    IReadOnlyDictionary<string, double>? Diagnostics = null);
 
 /// <summary>Driver-instance lifecycle state.</summary>
 public enum DriverState