feat(opcuaclient): #676 follow-ups — endpoint rewrite, stall wire test, fast definitive-loss recovery

- Endpoint rewrite: the driver now connects to the configured host AND port (scheme
  match, advertised path kept) instead of the server-advertised URL — fixes NAT/port-map
  upstreams and lets an in-test proxy carry the session (SDK SelectEndpoint rule).
- TcpStallProxy + OpcUaClientDriverStallWireTests: the in-place blip (#670) is now
  wire-tested on loopback — one Bad, frozen read stamp, same session, identical value
  republished Good, a post-recovery change arrives, no source-time regression after
  the SDK's late backlog flush.
- Defect found by that test, fixed: a change published right after a stall rode a
  Publish response the SDK timed out and never republished, leaving the node Good on
  the pre-change value indefinitely. New trailing reconcile read (Timeout +
  KeepAliveInterval after recovery) publishes any Good value newer than the last
  accepted one, through the replay guard's mark.
- IDriverConnectionLossSource (Core.Abstractions): opt-in definitive-loss signal.
  DriverInstanceActor attaches in PreStart / detaches in PostStop and turns a raise
  into a disconnect only while Connected. OpcUaClient raises once per session on
  keep-alive BadSessionIdInvalid/BadSessionClosed/BadSessionNotActivated/
  BadServerHalted (measured: the SDK never re-opens a halted channel) or a dropped
  subscription; ambiguous codes stay with the #527 watchdog.
- Replay guard: one Information summary per recovery when the window closes
  ("dropped N late notifications across M refs"), with a timer so quiet
  subscriptions log it too.
- ReconnectPeriod deleted (options, AdminUI form, docs, tests); stored configs that
  carry reconnectPeriod still parse in the factory, probe and browser.
- Docs: OpcUaClient.md, DriverLifecycle.md, driver-specs.md, CLAUDE.md.

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Browser.Tests/OpcUaClientDriverBrowserTests.cs

@@ -137,4 +137,17 @@ public sealed class OpcUaClientDriverBrowserTests
         sut.LastUsedUtc.ShouldBeGreaterThan(before,
             "AttributesAsync must refresh LastUsedUtc to satisfy the IBrowseSession contract");
     }
+
+    /// <summary>
+    ///     #676: a config still carrying the deleted <c>reconnectPeriod</c> key must deserialise — the browser's own
+    ///     validation (here: Certificate auth refused) is what fires, not a JSON error.
+    /// </summary>
+    [Fact]
+    public async Task OpenAsync_with_a_legacy_reconnectPeriod_key_still_parses()
+    {
+        var json = """{"EndpointUrl":"opc.tcp://127.0.0.1:1","reconnectPeriod":"00:00:05","AuthType":"Certificate"}""";
+        var ex = await Should.ThrowAsync<InvalidOperationException>(
+            () => _sut.OpenAsync(json, TestContext.Current.CancellationToken));
+        ex.Message.ShouldContain("Certificate");
+    }
 }