fix: wait for AutoCAD command-queue readiness barrier

Plant3D2026/P_Rec_Annot/src/PRecAnnot.Plant3D2026/FirstLimitedApplyAutomation.cs

@@ -204,7 +204,7 @@ internal sealed class FirstLimitedApplyAutomationCoordinator
             {
                 fixtureDocumentActivated = true;
                 transitions.Add("FixtureDocumentActiveAfterOpen");
-                TryActivateProjectAndVerifyContext();
+                QueueReadinessBarrier();
             }
         }
         catch (System.Exception ex) { FailFromCallback("Start", ex, "AUTOMATION_START_FAILED"); }
@@ -270,11 +270,23 @@ internal sealed class FirstLimitedApplyAutomationCoordinator
         transitions.Add("CommandQueued:" + command);
         document.SendStringToExecute(command + " ", true, false, false);
     }
+    private void QueueReadinessBarrier()
+    {
+        if (IsTerminal || document is null) return;
+        transitions.Add("ReadinessBarrierQueued");
+        document.SendStringToExecute("PHP_REC_AUTOMATION_READY ", true, false, false);
+    }
     private void OnCommandEnded(object sender, CommandEventArgs e)
     {
         RunCallback("CommandEnded", () =>
         {
             var name = e.GlobalCommandName?.Trim().TrimStart('.', '_').ToUpperInvariant();
+            if (name == "PHP_REC_AUTOMATION_READY")
+            {
+                transitions.Add("ReadinessBarrierCompleted");
+                TryActivateProjectAndVerifyContext();
+                return;
+            }
             if (name is not ("PXP-OA" or "UNDO" or "U")) return;
             completed.Add(name);
             transitions.Add("CommandCompleted:" + name);