fix(store-and-forward): resolve StoreAndForward-015..017 — document maxRetries=0 contract, replicate operator retry/discard, real category in activity log

src/ScadaLink.StoreAndForward/StoreAndForwardMessage.cs

@@ -27,7 +27,12 @@ public class StoreAndForwardMessage
     /// </summary>
     public int RetryCount { get; set; }
 
-    /// <summary>Maximum retry-sweep attempts before parking (0 = no limit).</summary>
+    /// <summary>
+    /// Maximum retry-sweep attempts before the message is parked.
+    /// <c>0</c> = no limit — the message is retried on every sweep until delivered
+    /// and is never parked for exhausting retries. This is <b>not</b> a "never retry"
+    /// value; a positive value is required to bound delivery attempts.
+    /// </summary>
     public int MaxRetries { get; set; }
 
     /// <summary>Retry interval in milliseconds.</summary>