Merge #591: FOCAS duplicate-sibling tests wait for the first axis pass, not the bootstrap stamp

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

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.FOCAS.Tests/FocasDuplicateSiblingNameTests.cs

@@ -53,10 +53,24 @@ public sealed class FocasDuplicateSiblingNameTests
     {
         var drv = NewDriver(tags);
         await drv.InitializeAsync("{}", CancellationToken.None);
-        var deadline = DateTime.UtcNow + TimeSpan.FromSeconds(5);
-        while (DateTime.UtcNow < deadline && drv.GetDeviceState(Host)?.LastFixedPollUtc is null)
-            await Task.Delay(25, TestContext.Current.CancellationToken);
-        drv.GetDeviceState(Host)!.LastFixedPollUtc.ShouldNotBeNull("the fixed-tree loop never completed a poll");
+        // LastFixedPollUtc alone is NOT "the first axis pass finished": the bootstrap stamps it
+        // after the sysinfo probe, before any axis snapshot is published (#591 — under load a
+        // read slipped into that window and saw BadNodeIdUnknown). Wait for the data itself:
+        // the last axis slot plus the servo/spindle caches this fake's first tick populates.
+        var deadline = DateTime.UtcNow + TimeSpan.FromSeconds(30);
+        var ready = false;
+        while (!ready && DateTime.UtcNow < deadline)
+        {
+            var st = drv.GetDeviceState(Host);
+            ready = st is not null
+                && st.LastFixedPollUtc is not null
+                && st.LastFixedSnapshots.ContainsKey(FocasDriver.FixedTreeReference(Host, "Axes/AA_2/AbsolutePosition"))
+                && st.LastServoLoads.Count >= 3
+                && st.LastSpindleLoads.Count >= 2
+                && st.LastSpindleMotorSpeeds.Count >= 2;
+            if (!ready) await Task.Delay(10, TestContext.Current.CancellationToken);
+        }
+        ready.ShouldBeTrue("the fixed-tree loop never completed its first full poll");
         return drv;
     }