feat(otopcua): set Modbus/S7/Galaxy re-discovery policy to Once + Once-branch test (follow-up B)

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.AbLegacy.Tests/AbLegacyDriverTests.cs

@@ -18,6 +18,17 @@ public sealed class AbLegacyDriverTests
         drv.DriverInstanceId.ShouldBe("drv-1");
     }
 
+    /// <summary>
+    ///     Verifies AbLegacy opts into run-once post-connect re-discovery — it discovers its
+    ///     complete node set synchronously from config, with no FOCAS-style background cache fill.
+    /// </summary>
+    [Fact]
+    public void RediscoverPolicy_is_Once()
+    {
+        var drv = new AbLegacyDriver(new AbLegacyDriverOptions(), "drv-1");
+        drv.RediscoverPolicy.ShouldBe(DiscoveryRediscoverPolicy.Once);
+    }
+
     /// <summary>Verifies that InitializeAsync with devices assigns family profiles.</summary>
     [Fact]
     public async Task InitializeAsync_with_devices_assigns_family_profiles()