feat(abcip): final review I1 — node-level Drivers:AbCip:DefaultTransport

The old AdminUI cannot author the per-driver transport key (#576), so the
'pin before upgrading' recipe had no working path. A node-level appsetting
(env Drivers__AbCip__DefaultTransport) now supplies the default for AbCip
drivers with no key: explicit key > node default > compiled Native. Bound
and validated unconditionally (bad value fails host start); the driver
factory and the Test Connect probe both read it so they agree. AbCip.md
upgrade recipe rewritten around the key; Configuration.md documents it.
Also documents first-wins for AllowPacking/probe and host-alias throttles
(final review M6) and moves the status-bit note out of AbCip.md (M5).

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

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.AbCip/AbCipDriverProbe.cs

@@ -34,11 +34,22 @@ public sealed class AbCipDriverProbe : IDriverProbe
     };
 
     private readonly IAbCipTagFactory? _tagFactory;
+    private readonly AbCipTransport _defaultTransport;
 
     /// <summary>Initializes a new instance of the <see cref="AbCipDriverProbe"/> class.</summary>
     /// <param name="tagFactory">Factory for the probe's tag runtime; when null the config's
     ///     <c>Transport</c> selects the native or libplctag-backed one.</param>
-    public AbCipDriverProbe(IAbCipTagFactory? tagFactory = null) => _tagFactory = tagFactory;
+    /// <param name="defaultTransport">The node-level default for a config with no <c>transport</c> key — the
+    ///     SAME value the node's driver factory uses, so Test Connect probes the stack the driver would run.</param>
+    public AbCipDriverProbe(IAbCipTagFactory? tagFactory = null,
+        AbCipTransport defaultTransport = AbCipTransportResolver.Default)
+    {
+        _tagFactory = tagFactory;
+        _defaultTransport = defaultTransport;
+    }
+
+    /// <summary>The node-level default this probe resolves an absent key to (wiring tests).</summary>
+    public AbCipTransport DefaultTransport => _defaultTransport;
 
     /// <inheritdoc />
     public string DriverType => "AbCip";
@@ -123,7 +134,7 @@ public sealed class AbCipDriverProbe : IDriverProbe
             ConnectionSize: firstDevice?.ConnectionSize ?? profile.DefaultConnectionSize,
             UseConnectedMessaging: profile.SupportsConnectedMessaging);
 
-        var rt = (_tagFactory ?? AbCipTransportFactories.For(AbCipTransportResolver.Resolve(opts)).Tags).Create(p);
+        var rt = (_tagFactory ?? AbCipTransportFactories.For(AbCipTransportResolver.Resolve(opts, _defaultTransport)).Tags).Create(p);
         try
         {
             await rt.InitializeAsync(cts.Token);