fix(alarms): atomic InactiveUnacknowledged + flagged Clear/Acknowledge first sight for OpcUaClient (#657)

After an OpcUaClient respawn an upstream inactive+unacked condition went out as
Retrigger+Clear (duplicate Activated+Cleared rows, Active flicker), and a
first-sight inactive+acked one as Unspecified (an Activated row for an inactive
alarm; a retained-Active host condition never cleared).

- New AlarmTransitionKind.InactiveUnacknowledged: one projection, rows only for
  what changed (Activated+Cleared from acked, Cleared from active+unacked, none
  when already inactive+unacked).
- OpcUaClient uses it for moves into inactive+unacked; first sight of an
  inactive condition is InactiveUnacknowledged or Clear+Acknowledge, flagged.
- Projector: a flagged Acknowledge on an already-acked condition writes no row.
- E2E tests through DriverHostActor.ForwardNativeAlarm (red-proven).

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

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient/OpcUaClientDriver.cs

@@ -2069,7 +2069,7 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
     /// <summary>
     ///     #619 review — the <see cref="AlarmTransitionKind"/> sequence that moves the host's
     ///     <c>NativeAlarmProjector</c> (which knows only kinds: Raise ⇒ active+unacked — or, on an already-active condition, a re-statement keeping the ack (#647) — Acknowledge ⇒ acked,
-    ///     ActiveAcknowledged ⇒ active+acked in one step (#656), Clear ⇒ inactive keeping acked) from <paramref name="prior"/> to <paramref name="target"/>. A single
+    ///     ActiveAcknowledged ⇒ active+acked in one step (#656), InactiveUnacknowledged ⇒ inactive+unacked in one step (#657), Clear ⇒ inactive keeping acked) from <paramref name="prior"/> to <paramref name="target"/>. A single
     ///     upstream event can need two (an alarm that went active and was acknowledged between two notifications).
     ///     No state change ⇒ empty (the caller decides whether a message/severity change warrants an Unspecified).
     /// </summary>
@@ -2086,6 +2086,16 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
     internal static IReadOnlyList<AlarmTransitionKind> AlarmTransitions(
         (bool Active, bool Acked) prior, (bool Active, bool Acked) target, bool priorKnown = true)
     {
+        // Gitea #657: on first sight the host may hold ANY state (it retains a still-deployed condition across a
+        // respawn), so an inactive target is stated in kinds that land on it from every host state: inactive+unacked
+        // as ONE InactiveUnacknowledged; inactive+acked as Clear then Acknowledge (flagged by the caller, so a host
+        // already showing it writes no row, and a host retaining it Active gets a real "Cleared"). Pre-fix an
+        // inactive+acked first sight equalled the default prior and went out as Unspecified — an "Activated" row for
+        // an inactive alarm, and a retained-Active host condition was never cleared.
+        if (!priorKnown && !target.Active)
+            return target.Acked
+                ? [AlarmTransitionKind.Clear, AlarmTransitionKind.Acknowledge]
+                : [AlarmTransitionKind.InactiveUnacknowledged];
         if (prior == target) return [];
         var kinds = Transitions(prior, target);
         return priorKnown || target.Acked
@@ -2109,11 +2119,12 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
             (false, true) => prior.Active
                 ? prior.Acked ? [AlarmTransitionKind.Clear] : [AlarmTransitionKind.Clear, AlarmTransitionKind.Acknowledge]
                 : [AlarmTransitionKind.Acknowledge],
-            // Inactive+UNacked (went active and cleared unacknowledged — e.g. first seen by a ConditionRefresh):
-            // the only kinds that un-ack are Raise/Retrigger, so pass through active, then Clear.
-            (false, false) => prior.Active
-                ? prior.Acked ? [AlarmTransitionKind.Retrigger, AlarmTransitionKind.Clear] : [AlarmTransitionKind.Clear]
-                : [AlarmTransitionKind.Raise, AlarmTransitionKind.Clear],
+            // Inactive+UNacked (went active and cleared unacknowledged — e.g. first seen by a ConditionRefresh): ONE
+            // atomic InactiveUnacknowledged (Gitea #657) — Raise/Retrigger-then-Clear showed clients the condition
+            // Active again for an instant. From Active+unacked a plain Clear already lands there.
+            (false, false) => prior is (true, false)
+                ? [AlarmTransitionKind.Clear]
+                : [AlarmTransitionKind.InactiveUnacknowledged],
         };
     }