fix(sitecallaudit): UpdatedAtUtc index + per-row pull resilience + UTC-convention + first-cycle test (review)

src/ZB.MOM.WW.ScadaBridge.SiteRuntime/Tracking/OperationTrackingStore.cs

@@ -91,6 +91,8 @@ public class OperationTrackingStore : IOperationTrackingStore, IAsyncDisposable,
             );
             CREATE INDEX IF NOT EXISTS IX_OperationTracking_Status_Updated
                 ON OperationTracking (Status, UpdatedAtUtc);
+            CREATE INDEX IF NOT EXISTS IX_OperationTracking_UpdatedAt
+                ON OperationTracking (UpdatedAtUtc);
             """;
         cmd.ExecuteNonQuery();
 
@@ -370,8 +372,10 @@ public class OperationTrackingStore : IOperationTrackingStore, IAsyncDisposable,
 
         // SiteRuntime-024: like GetStatusAsync, the reconciliation pull opens a
         // fresh, ungated read connection so a long-running write never blocks
-        // central's PullSiteCalls. The query is a bounded, ordered scan over the
-        // (Status, UpdatedAtUtc) index range — UpdatedAtUtc is the cursor.
+        // central's PullSiteCalls. The query is a bounded, ordered scan served by
+        // the standalone IX_OperationTracking_UpdatedAt index — UpdatedAtUtc is
+        // the cursor. (The composite (Status, UpdatedAtUtc) index cannot satisfy a
+        // status-less UpdatedAtUtc range scan; this dedicated index does.)
         await using var readConnection = new SqliteConnection(_connectionString);
         await readConnection.OpenAsync(ct).ConfigureAwait(false);
 
@@ -390,9 +394,15 @@ public class OperationTrackingStore : IOperationTrackingStore, IAsyncDisposable,
             ORDER  BY UpdatedAtUtc ASC
             LIMIT  $batchSize;
             """;
-        cmd.Parameters.AddWithValue(
-            "$since",
-            sinceUtc.ToString("o", CultureInfo.InvariantCulture));
+        // Force UTC kind before formatting so the cursor's "o" text matches the
+        // 'Z'-suffixed round-trip form the write path persists (DateTime.UtcNow
+        // .ToString("o")). A first-cycle DateTime.MinValue arrives Unspecified —
+        // without this its "o" rendering would lack the 'Z', and the SQLite text
+        // compare against 'Z'-suffixed stored values would be subtly inconsistent.
+        var sinceText = DateTime
+            .SpecifyKind(sinceUtc, DateTimeKind.Utc)
+            .ToString("o", CultureInfo.InvariantCulture);
+        cmd.Parameters.AddWithValue("$since", sinceText);
         cmd.Parameters.AddWithValue("$batchSize", batchSize);
 
         var rows = new List<SiteCallOperational>();