fix(cluster): ClusterRoleInfo._roleLeaders stays Ordinal — Akka tracks role-leadership per exact gossiped role string (review finding, R3-04)

src/Core/ZB.MOM.WW.OtOpcUa.Cluster/ClusterRoleInfo.cs

@@ -23,12 +23,21 @@ public sealed class ClusterRoleInfo : IClusterRoleInfo, IDisposable
     private readonly string? _clusterRole;
     private readonly string? _clusterId;
     private readonly object _lock = new();
-    // R3-04 (01/C-9, census row 17): OrdinalIgnoreCase — Akka compares gossiped role names ordinally,
-    // so a PEER running an older build can still gossip a miscased plain role during a rolling
-    // upgrade. Keying these by the exact-cased role string would leave MembersWithRole("driver") and
-    // RoleLeader("driver") blind to a peer that gossips "Driver", the same class of gap #532 closed
-    // for _localRoles above.
-    private readonly Dictionary<string, Member?> _roleLeaders = new(StringComparer.OrdinalIgnoreCase);
+    // R3-04 (01/C-9, census row 17) — the two dictionaries below have DIFFERENT correct comparers,
+    // and that split is deliberate, not an oversight (review finding, 2026-08-20).
+    //
+    // _membersByRole answers "every member carrying (a spelling of) this role" — OrdinalIgnoreCase,
+    // so a PEER running an older build that still gossips a miscased plain role during a rolling
+    // upgrade is not invisible to MembersWithRole("driver"). Merging casings IS the point here.
+    //
+    // _roleLeaders must stay Ordinal. Akka computes — and raises RoleLeaderChanged for — role
+    // leadership PER EXACT GOSSIPED ROLE STRING: "driver" and "Driver" are two entirely distinct
+    // roles to Akka's own role-leader machinery, each independently electing its own leader. An
+    // OrdinalIgnoreCase dictionary here would collapse both onto ONE key, so whichever
+    // RoleLeaderChanged event landed last would silently overwrite the other's leader — turning two
+    // real, independent facts Akka tracks separately into one, wrong, merged one. Pinned by
+    // ClusterRoleInfoRoleLeaderCaseTests.RoleLeaderChanged_for_driver_then_Driver_keeps_distinct_entries.
+    private readonly Dictionary<string, Member?> _roleLeaders = new(StringComparer.Ordinal);
     private readonly Dictionary<string, HashSet<Member>> _membersByRole = new(StringComparer.OrdinalIgnoreCase);
     private IActorRef? _subscriber;