fix(store-and-forward): resolve StoreAndForward-003, re-triage 002 — fix retry-count off-by-one

src/ScadaLink.StoreAndForward/StoreAndForwardService.cs

@@ -148,13 +148,14 @@ public class StoreAndForwardService
             }
             catch (Exception ex)
             {
-                // Transient failure — buffer for retry
+                // Transient failure — buffer for retry. The immediate attempt is
+                // attempt 0; RetryCount tracks only sweep retries, so it stays 0
+                // here (StoreAndForward-003).
                 _logger.LogWarning(ex,
                     "Immediate delivery to {Target} failed (transient), buffering for retry",
                     target);
 
                 message.LastAttemptAt = DateTimeOffset.UtcNow;
-                message.RetryCount = 1;
                 message.LastError = ex.Message;
                 await BufferAsync(message);
 
@@ -165,11 +166,11 @@ public class StoreAndForwardService
 
         // Either no handler is registered yet, or the caller already attempted
         // delivery itself — buffer for the background retry sweep to deliver.
+        // The initial attempt (caller-made, or skipped because no handler is
+        // registered) is attempt 0; RetryCount tracks only sweep retries and
+        // therefore stays 0 here (StoreAndForward-003).
         if (!attemptImmediateDelivery)
         {
-            // The caller made (and failed) one attempt before handing the
-            // message over, so it counts as the first retry.
-            message.RetryCount = 1;
             message.LastAttemptAt = DateTimeOffset.UtcNow;
         }
         await BufferAsync(message);