fix(core-abstractions): resolve Low code-review findings (Core.Abstractions-004,005,006,007,008)

- Core.Abstractions-004: guard DriverTypeRegistry.Register with a Lock so
  concurrent registrations are atomic.
- Core.Abstractions-005: narrow PollGroupEngine catch blocks to non-fatal
  exceptions, add optional onError callback, tolerate disposed-CTS races.
- Core.Abstractions-006: document the deliberate int-vs-uint asymmetry on
  IHistoryProvider.ReadEventsAsync / IHistorianDataSource.ReadEventsAsync.
- Core.Abstractions-007: pin the gaps with PollGroupEngine + DriverHealth
  contract tests.
- Core.Abstractions-008: correct XML docs on DriverHealth.LastError and
  the optional / required asymmetry on the history-read surfaces.

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

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

@@ -6,7 +6,15 @@ namespace ZB.MOM.WW.OtOpcUa.Core.Abstractions;
 /// </summary>
 /// <param name="State">Current driver-instance state.</param>
 /// <param name="LastSuccessfulRead">Timestamp of the most recent successful equipment read; null if never.</param>
-/// <param name="LastError">Most recent error message; null when state is Healthy.</param>
+/// <param name="LastError">
+///     Most recent error message; null when no error has been recorded. The type makes no
+///     guarantee about correlation with <paramref name="State"/> — a driver in
+///     <see cref="DriverState.Healthy"/> may legitimately retain the last error from a recovered
+///     failure (useful for diagnostics), and <see cref="DriverState.Degraded"/> /
+///     <see cref="DriverState.Reconnecting"/> / <see cref="DriverState.Faulted"/> states may all
+///     carry a non-null message. Callers must not key behaviour on the LastError-null ↔ Healthy
+///     pairing (Core.Abstractions-008).
+/// </param>
 public sealed record DriverHealth(
     DriverState State,
     DateTime? LastSuccessfulRead,