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/checksum.c

@@ -223,17 +223,25 @@ bool checksum_digest_file(ChecksumAlgo algo, uint64_t seed, const char* path, ui
   if (fd < 0)
     return false;
 
+  if (algo == CHECKSUM_ALGO_NONE) {
+    /* No checksum requested: nothing to read; an empty digest succeeds. */
+    close(fd);
+    *out_len = 0;
+    return true;
+  }
+
   uint8_t buffer[64 * 1024];
   bool ok = false;
 
-  if (algo == CHECKSUM_ALGO_MD5) {
+  if (algo == CHECKSUM_ALGO_MD5 || algo == CHECKSUM_ALGO_SHA1) {
+    const EVP_MD* md = algo == CHECKSUM_ALGO_MD5 ? EVP_md5() : EVP_sha1();
     EVP_MD_CTX* ctx = EVP_MD_CTX_new();
     if (!ctx) {
       close(fd);
       return false;
     }
     unsigned int digest_len = 0;
-    if (EVP_DigestInit_ex(ctx, EVP_md5(), NULL) == 1) {
+    if (EVP_DigestInit_ex(ctx, md, NULL) == 1) {
       ok = true;
       ssize_t got;
       while ((got = read(fd, buffer, sizeof(buffer))) > 0) {
@@ -254,6 +262,23 @@ bool checksum_digest_file(ChecksumAlgo algo, uint64_t seed, const char* path, ui
     return ok;
   }
 
+  if (algo == CHECKSUM_ALGO_MD4) {
+    Md4Ctx ctx;
+    md4_init(&ctx);
+    ok = true;
+    ssize_t got;
+    while ((got = read(fd, buffer, sizeof(buffer))) > 0)
+      md4_update(&ctx, buffer, (size_t)got);
+    if (got < 0)
+      ok = false;
+    if (ok) {
+      md4_final(&ctx, out);
+      *out_len = 16;
+    }
+    close(fd);
+    return ok;
+  }
+
   XXH64_state_t xxh64;
   XXH3_state_t* xxh3 = NULL;
   if (algo == CHECKSUM_ALGO_XXH64) {