fix(parity): actual-removal delete-delay counts, rsync-accurate stats/progress/%C

- --delete-delay: count/track only entries actually removed; a directory
  refilled before commit (ENOTEMPTY) no longer inflates Number of deleted
  files or the --max-delete budget (unit + integration + rsync differential).
- --stats: per-type Number of files breakdown; only stored regular files
  count as transferred; transferred/literal byte totals and Total file size
  (symlink target lengths) now match rsync for whole-file transfers.
- --progress: print the leading ./ root line and include the root entry in
  the to-chk denominator (single-file output byte-identical to rsync).
- --out-format %C: use the selected transfer checksum and render every
  algorithm exactly like rsync; checksum_digest_file gains md4/sha1/none.
  Reclassify --out-format to Divergent (protocol-specific %b/delta-%c).
- Docs: RSYNC_COMPAT tally 107/25/24, HANDOFF update. No wire change.

src/shared/multiprocessing.h

@@ -9,6 +9,7 @@
 #include "config.h"
 #include "delete_plan.h"
 #include "file.h"
+#include "format.h"
 #include "protocol.h"
 #include "queue.h"
 #include "stop_condition.h"
@@ -86,6 +87,9 @@ typedef struct {
   int total_files;
   unsigned long long progress_bytes;
   unsigned long long total_bytes;
+  /* Per-type flist / transferred accounting for the rsync --stats breakdown and
+     the progress `to-chk` denominator.  Guarded by mutex_progress. */
+  TransferStats stats;
   bool sender_done;
   atomic_bool cancelled;
   ProtocolSession allocation_session;