fix(probe): bound AbLegacy handshake by timeout CTS + stop sw; correct FOCAS timeout comment (code-review)

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.AbLegacy/AbLegacyDriverProbe.cs

@@ -59,12 +59,17 @@ public sealed class AbLegacyDriverProbe : IDriverProbe
         var host = parsed.Gateway;
         var port = parsed.Port;
 
+        // Bound both phases by the caller timeout, independent of `ct`, so a device that accepts
+        // TCP but stalls the PCCC session cannot hang the probe.
+        using var cts = CancellationTokenSource.CreateLinkedTokenSource(ct);
+        cts.CancelAfter(timeout);
+
         // Phase 1: bare TCP preflight — fast rejection for unreachable hosts.
         var sw = Stopwatch.StartNew();
         try
         {
             using var socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
-            await socket.ConnectAsync(host, port, ct);
+            await socket.ConnectAsync(host, port, cts.Token);
         }
         catch (SocketException ex)
         {
@@ -104,7 +109,7 @@ public sealed class AbLegacyDriverProbe : IDriverProbe
         var rt = new LibplctagLegacyTagRuntime(p);
         try
         {
-            await rt.InitializeAsync(ct);
+            await rt.InitializeAsync(cts.Token);
             sw.Stop();
 
             // InitializeAsync completed without throwing — either the tag was found (Ok) or
@@ -129,7 +134,10 @@ public sealed class AbLegacyDriverProbe : IDriverProbe
         {
             // LibPlcTagException carries the Status; classify as reachable vs transport failure.
             if (IsReachableException(ex))
+            {
+                sw.Stop();
                 return new(true, "PCCC session OK (controller reachable; probe tag not found)", sw.Elapsed);
+            }
 
             return new(false, $"Reachable at {host}:{port} but PCCC handshake failed: {ex.Message}", null);
         }

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.FOCAS/FocasDriverProbe.cs

@@ -114,7 +114,9 @@ public sealed class FocasDriverProbe : IDriverProbe
         }
         catch (OperationCanceledException)
         {
-            // ct cancelled or the native handshake exceeded the timeout budget.
+            // The caller cancelled, or the Task.Run was cancelled before the native call started.
+            // (A native cnc_allclibhndl3 that is already running is bounded by the timeoutSeconds
+            // argument passed into it, not by handshakeCts — see TryAllocateAndFreeHandle.)
             return new(false, $"Probe timed out after {timeout.TotalSeconds:F0}s.", null);
         }
     }