Fix: preserve reverse_row_groups/reverse_rows across proto roundtrip

When PushdownSort removes SortExec and sets reverse_row_groups=true /
reverse_rows=true on ParquetSource, these runtime flags must survive
proto serialization. Without this, remote executors (RemoteExec) would
deserialize the plan without reverse scanning, producing wrong order.

Added reverse_row_groups and reverse_rows fields to ParquetScanExecNode
proto message, serialized on encode and restored on decode.

Author: zhuqi-lucas

datafusion/proto/proto/datafusion.proto

@@ -1058,6 +1058,12 @@ message ParquetScanExecNode {
   PhysicalExprNode predicate = 3;
 
   datafusion_common.TableParquetOptions parquet_options = 4;
+
+  // Runtime reverse-scan flags set by PushdownSort optimizer.
+  // Must be preserved across proto roundtrips so that remote executors
+  // produce correctly reversed output after SortExec removal.
+  bool reverse_row_groups = 5;
+  bool reverse_rows = 6;
 }
 
 message CsvScanExecNode {

datafusion/proto/src/generated/pbjson.rs

@@ -724,6 +724,14 @@ impl protobuf::PhysicalPlanNode {
             if let Some(predicate) = predicate {
                 source = source.with_predicate(predicate);
             }
+
+            // Restore runtime reverse-scan flags from proto
+            if scan.reverse_row_groups {
+                source = source.with_reverse_row_groups(true);
+            }
+            if scan.reverse_rows {
+                source = source.with_reverse_rows(true);
+            }
             let base_config = parse_protobuf_file_scan_config(
                 base_conf,
                 ctx,
@@ -2672,6 +2680,8 @@ impl protobuf::PhysicalPlanNode {
                         )?),
                         predicate,
                         parquet_options: Some(conf.table_parquet_options().try_into()?),
+                        reverse_row_groups: conf.reverse_row_groups(),
+                        reverse_rows: conf.reverse_rows(),
                     },
                 )),
             }));