Merge b647-focas-alarms: FOCAS native alarms reach Part 9 conditions (ALARM: address) + respawn keeps acks host-side (#647)

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

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

@@ -1942,12 +1942,11 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
 
             // Fresh prior = the host projector's own default (inactive, acked).
             var told = new AlarmToldState(target.Active, target.Acked, e.Message, e.OpcUaSeverity);
-            var prior = _alarmStateByRawPath.TryGetValue(e.ConditionId, out var p)
-                ? p
-                : new AlarmToldState(false, true, null, null);
+            var priorKnown = _alarmStateByRawPath.TryGetValue(e.ConditionId, out var p);
+            var prior = priorKnown ? p! : new AlarmToldState(false, true, null, null);
             _alarmStateByRawPath[e.ConditionId] = told;
 
-            var kinds = AlarmTransitions((prior.Active, prior.Acked), target);
+            var kinds = AlarmTransitions((prior.Active, prior.Acked), target, priorKnown);
             if (kinds.Count == 0)
             {
                 // Same state: a message/severity change still reaches the host; an identical copy does not.
@@ -2066,18 +2065,34 @@ 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, Acknowledge ⇒ acked,
+    ///     <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,
     ///     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>
     /// <param name="prior">The state last told to the host.</param>
     /// <param name="target">The upstream event's ActiveState/Id + AckedState/Id.</param>
+    /// <param name="priorKnown">
+    ///     False when this driver instance has told the host nothing about the condition yet (first sight after a
+    ///     start or a deploy respawn), so <paramref name="prior"/> is only the projector's default. Gitea #647 review:
+    ///     the host now treats a Raise on an already-active condition as a re-statement that KEEPS its ack, so an
+    ///     upstream that says <i>unacknowledged</i> must then be told with <see cref="AlarmTransitionKind.Retrigger"/>
+    ///     — the upstream's ack state is authoritative, and the host may be holding an ack from before the respawn.
+    /// </param>
     /// <returns>The kinds to emit, in order.</returns>
     internal static IReadOnlyList<AlarmTransitionKind> AlarmTransitions(
-        (bool Active, bool Acked) prior, (bool Active, bool Acked) target)
+        (bool Active, bool Acked) prior, (bool Active, bool Acked) target, bool priorKnown = true)
     {
         if (prior == target) return [];
+        var kinds = Transitions(prior, target);
+        return priorKnown || target.Acked
+            ? kinds
+            : [.. kinds.Select(k => k == AlarmTransitionKind.Raise ? AlarmTransitionKind.Retrigger : k)];
+    }
+
+    private static IReadOnlyList<AlarmTransitionKind> Transitions(
+        (bool Active, bool Acked) prior, (bool Active, bool Acked) target)
+    {
         return target switch
         {
             // Active+unacked: a fresh raise, or a re-arm of an active-acked condition.