test(otopcua): cover discovered-node rebind drop + clarify re-apply scope

src/Server/ZB.MOM.WW.OtOpcUa.Runtime/Drivers/DriverHostActor.cs

@@ -1245,11 +1245,14 @@ public sealed class DriverHostActor : ReceiveActor, IWithTimers
         _lastComposition = composition;
 
         // Re-inject discovered (FixedTree) nodes after the authored rebuild. PushDesiredSubscriptions cleared
-        // _nodeIdByDriverRef and re-pushed authored-only subscriptions above; without this, every redeploy /
-        // bootstrap-restore would drop the injected FixedTree routes + materialised nodes until the driver
-        // happens to reconnect and re-discover. Re-resolve each cached driver's equipment from the CURRENT
-        // composition; drop the cache entry if the driver/equipment no longer resolves to exactly one (a rebind
-        // or removal — the driver's next reconnect re-discovery will rebuild it cleanly).
+        // _nodeIdByDriverRef and re-pushed authored-only subscriptions above; without this, an IN-PROCESS
+        // redeploy / re-apply (one that runs while the host is alive, so _discoveredByDriver is populated)
+        // would drop the injected FixedTree routes + materialised nodes until the driver happens to reconnect
+        // and re-discover. This loop is INERT on the bootstrap-restore path (RestoreApplied): there the actor
+        // is freshly constructed so _discoveredByDriver is empty — restart survival comes from Task 6's
+        // post-connect re-discovery, NOT this re-apply. Re-resolve each cached driver's equipment from the
+        // CURRENT composition; drop the cache entry if the driver/equipment no longer resolves to exactly one
+        // (a rebind or removal — the driver's next reconnect re-discovery will rebuild it cleanly).
         foreach (var driverId in _discoveredByDriver.Keys.ToList())   // snapshot — we mutate the dict below
         {
             var plan = _discoveredByDriver[driverId];
@@ -1267,6 +1270,14 @@ public sealed class DriverHostActor : ReceiveActor, IWithTimers
             var equipmentId = equipmentIds[0];
             // If the equipment was rebound (the cached plan's NodeIds are scoped to the OLD equipment), drop +
             // let re-discovery rebuild against the new equipment. The plan's NodeIds are "{equipmentId}/...".
+            // KNOWN LIMITATION (follow-up, alongside the multi-device-per-driver limitation): a
+            // CONFIG-UNCHANGED rebind (the driver's DriverConfig is identical, only its authored tag's
+            // EquipmentId moved) drops the cached plan here but does NOT itself re-trigger discovery —
+            // ReconcileDrivers only restarts a child on a DriverConfig change, so a config-unchanged child is
+            // never stopped/reconnected. The FixedTree subtree therefore stays ABSENT under the new equipment
+            // until the driver's next reconnect/restart re-discovers it. We deliberately do NOT add re-trigger
+            // logic here (it would couple the subscription pass to driver-lifecycle control); the drop is the
+            // safe, correct fail-state (a stale EQ-1-scoped graft under EQ-2 would be worse).
             var planEquipmentConsistent = plan.Variables.Count > 0
                 && plan.Variables[0].NodeId.StartsWith(equipmentId + "/", StringComparison.Ordinal);
             if (!planEquipmentConsistent)