fix(data-connection): resolve DataConnectionLayer-006..012 — quality-counter reconciliation, per-tag batch reads, configurable failover threshold, dedup retry, stale-callback guard, secure cert default

src/ScadaLink.DataConnectionLayer/Adapters/OpcUaDataConnection.cs

@@ -186,10 +186,26 @@ public class OpcUaDataConnection : IDataConnection
 
     public async Task<IReadOnlyDictionary<string, ReadResult>> ReadBatchAsync(IEnumerable<string> tagPaths, CancellationToken cancellationToken = default)
     {
+        // DataConnectionLayer-007: a single failing tag must not abort the whole batch.
+        // ReadAsync re-throws non-cancellation exceptions; catch them per tag and record
+        // a failed ReadResult so the caller receives a complete result map for every
+        // requested tag (the ReadResult shape already carries per-tag Success/error).
         var results = new Dictionary<string, ReadResult>();
         foreach (var tagPath in tagPaths)
         {
-            results[tagPath] = await ReadAsync(tagPath, cancellationToken);
+            try
+            {
+                results[tagPath] = await ReadAsync(tagPath, cancellationToken);
+            }
+            catch (OperationCanceledException)
+            {
+                // Cancellation aborts the whole batch — propagate it.
+                throw;
+            }
+            catch (Exception ex)
+            {
+                results[tagPath] = new ReadResult(false, null, ex.Message);
+            }
         }
         return results;
     }