test(delete): differential + timing regression tests for per-directory delete plans

- Compare --delete-during/--delete-delay final state against rsync 3.4.1.
- Force a mid-transfer failure through a byte-slicing proxy: --delete-during has
  removed the processed directory's extra, --delete-delay has not.
- Create a destination entry while the transfer is in flight: it survives
  --delete-delay's snapshot but is removed by --delete-after's fresh end scan.
- Cover the --delete-delay type-conflict case now matching rsync.

src/server/receiver.c

@@ -259,8 +259,7 @@ int receiver_process(Config* config, int file_descriptor, const ReceiverSink* si
    the whole transfer succeeded.  See receiver_process_pending() for how the -m
    receiver defers that commit until its disk writer has drained. */
 int receiver_process_pending(Config* config, int file_descriptor, const ReceiverSink* sink,
-                             DeleteManifest** pending_manifest,
-                             DeletePlanSession** pending_plans) {
+                             DeleteManifest** pending_manifest, DeletePlanSession** pending_plans) {
   Status status;
   if (!receive_status(file_descriptor, &status))
     return -1;