fix: revert AffectedRows/RowCount default back to 0

Reverts the ?? -1 change back to ?? 0 for both ExecuteQuery and
ExecuteUpdate. SEA API returns 0 for DDL, not -1. Keeping original
SEA behavior.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: msrathore-db

csharp/src/StatementExecution/StatementExecutionStatement.cs

@@ -304,8 +304,8 @@ public async Task<QueryResult> ExecuteQueryAsync(
             // Get schema from reader
             var schema = reader.Schema;
 
-            // Return query result - use -1 if row count is not available
-            long rowCount = response.Manifest?.TotalRowCount ?? -1;
+            // Return query result - use 0 if row count is not available
+            long rowCount = response.Manifest?.TotalRowCount ?? 0;
             return new QueryResult(rowCount, reader);
         }
 
@@ -626,8 +626,7 @@ public async Task<UpdateResult> ExecuteUpdateAsync(CancellationToken cancellatio
             }
 
             // For updates, we don't need to read the results - just return the row count.
-            // Default to -1 (unknown) when no manifest/row count, matching Thrift behavior for DDL.
-            long rowCount = response.Manifest?.TotalRowCount ?? -1;
+            long rowCount = response.Manifest?.TotalRowCount ?? 0;
             return new UpdateResult(rowCount);
         }