feat(browse): Wave-0 Batch B — AbCip/TwinCAT/FOCAS opt into online discovery

Task 3/4/5: SupportsOnlineDiscovery => true on AbCipDriver, TwinCATDriver, FocasDriver
(their device enumeration is real, config-gated on EnableControllerBrowse / FixedTree.Enabled
which PatchForBrowse guarantees at open). One gate fact per driver test project.

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

@@ -999,6 +999,10 @@ public sealed class AbCipDriver : IDriver, IReadable, IWritable, ITagDiscovery,
     /// <inheritdoc />
     public DiscoveryRediscoverPolicy RediscoverPolicy => DiscoveryRediscoverPolicy.Once;
 
+    /// <summary>Controller enumeration is real (CIP Symbol Object walk) — config-gated on
+    /// EnableControllerBrowse, which the universal browser's PatchForBrowse guarantees at open time.</summary>
+    public bool SupportsOnlineDiscovery => true;
+
     /// <inheritdoc />
     public async Task DiscoverAsync(IAddressSpaceBuilder builder, CancellationToken cancellationToken)
     {