fix(twincat): string subscriptions, Windows-1252 STRING decode, and declared-type kind checks (ignitionoee 0.19.2-0.19.4)

Port of the ignitionoee TwinCAT string + type-reconciliation fixes onto the
Beckhoff-library client:

- STRING/WSTRING subscriptions never worked: AddDeviceNotificationExAsync was
  called with typeof(string) and no length, and the Beckhoff any-type
  marshaller throws ArgumentNullException for a string without one, so one
  string tag tore down its whole subscribe call. A string now registers the
  PLC's own byte width as raw bytes (0.19.2: STRING(n) of any n).
- Strings are read as raw bytes and decoded by TwinCATStringCodec. The
  Beckhoff marshaller already cut a read at the first NUL (0.19.3 / TwinCAT-007
  were not defects on the read path); the codec keeps that rule for both STRING
  and WSTRING and extends it to the new notification path. A STRING now decodes
  as Windows-1252 (TwinCAT-010) - or UTF-8 when the target reports UTF-8
  strings - instead of the host culture's ANSI code page the Beckhoff
  marshaller falls back to (1250 on a Polish host, 1251 Cyrillic, ...).
- TwinCATTypeGuard (TwinCAT-002/-008): a read refuses a numeric tag over a PLC
  string (and vice versa / STRING vs WSTRING / string over a container) with
  BadTypeMismatch instead of handing back a string object at Good; a
  notification - raw bytes decoded as the DECLARED type - additionally refuses
  width and float/integer mismatches (DINT over REAL reinterpreted the bits).
- A refused notification is isolated: that tag publishes BadTypeMismatch with
  one WARN, keeps a dead intent for the probe-tick retry, and the rest of the
  subscription registers.

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.TwinCAT/ITwinCATClient.cs

@@ -94,6 +94,9 @@ public interface ITwinCATClient : IDisposable
     /// <param name="onChange">Invoked with <c>(symbolPath, boxedValue)</c> per notification.</param>
     /// <param name="cancellationToken">Cancels the initial registration; does not tear down an established notification.</param>
     /// <returns>A handle whose disposal tears the registered notification down.</returns>
+    /// <exception cref="TwinCATTypeMismatchException">The declared <paramref name="type"/> cannot decode
+    ///     the PLC symbol (width, float/integer or string kind differ) — the caller isolates that one tag
+    ///     to Bad rather than registering a notification that would publish wrong bytes at Good.</exception>
     Task<ITwinCATNotificationHandle> AddNotificationAsync(
         string symbolPath,
         TwinCATDataType type,