Adds a filter-aware overload of IHistoryProvider.ReadEventsAsync that carries
EventFilter SelectClauses + WhereClause, and implements it on the OPC UA
Client driver via Session.HistoryReadAsync + ReadEventDetails.
The change is additive (default-impl returns NotSupportedException) so the
existing Galaxy.Proxy.GalaxyProxyDriver implementation keeps compiling
against the fixed-field overload — no cross-driver refactor required.
* Core.Abstractions: new EventHistoryRequest / SimpleAttributeSpec /
ContentFilterSpec records mirror the OPC UA wire shape transport-neutrally.
HistoricalEventBatch / HistoricalEventRow carry an open-ended Fields bag
keyed by SimpleAttributeSpec.FieldName so server-side dispatch can re-align
with the client's wire-side SelectClause order.
* OpcUaClient driver: new ReadEventsAsync(fullReference, EventHistoryRequest, ct)
builds an EventFilter, calls Session.HistoryReadAsync, and unwraps
HistoryEvent.Events into HistoricalEventBatch rows. Default SelectClause
set matches BuildHistoryEvent on the server side. ContentFilter bytes are
decoded through the live session's MessageContext (passthrough — the
driver does not evaluate filters).
* Unit tests: 7 new tests cover SelectClause translation, default-clause
fallback, malformed where-clause swallowing, uninitialized-driver guard,
null-request guard, and IHistoryProvider default fallback.
* Integration scaffold: build-only [Fact] gated on opc-plc --alm; flips to
green when the fixture image is upgraded.
* Docs: HistoryRead Events section in docs/drivers/OpcUaClient.md plus a
cross-link from Client.CLI.md historyread page.
* E2E: -HistoryEvents switch on scripts/e2e/test-opcuaclient.ps1 confirms
the gateway round-trips HistoryReadEvents without
BadHistoryOperationUnsupported (gated; defaults to skip).
Closes#284
c36903d6a0