fix: address c-review for -R/--dirs/--mkpath row

B1: destination-root existence/creation mishandled two legitimate forms.
file_directory_exists_secure/file_ensure_directory_secure now normalize a
trailing-slash destination (so the last component is never an empty leaf)
and treat a destination equal to the already-open authorized root as present
(no spurious <root>/<basename> nested dir with --mkpath). Confinement and
O_NOFOLLOW probing are unchanged. Regression integration tests: existing
dest with trailing slash works with and without --mkpath; dest == authorized
root works and creates no stray nested dir.

W1: chunk serialize/deserialize round-trip unit test for a directory entry
mixed with a regular file, with and without metadata; --dirs coverage under
-s and -s -m.
W2: --list-only and --dry-run now print file_wire_path() so all outputs show
the -R transformed relative name, matching -i/--out-format.
W3: RSYNC_COMPAT -d/--dirs note: dirs are created immediately under
--delay-updates (only regular files are staged).
W4: --dirs generator flushes chunks by element count too, so a long
--files-from list of empty directories cannot exceed the per-chunk file cap.
N1: STATUS_MKDIR added to status_to_string.
N2: removed dead TestMkpath._transfer.
N3: removed redundant --no-implied-dirs OPTION_TABLE row.
N4: integration tests: --dirs --delete keeps the just-created empty dir (and
deletes extras); a listed dir colliding with a regular file at the dest fails
cleanly.

src/client/client_send.c

@@ -435,7 +435,8 @@ static int send_dry_run_manifest(const Config* config) {
   while ((chunk = directory_scanner_next(scanner)) != NULL) {
     for (int i = 0; i < chunk->element_count; i++) {
       if (!config->quiet) {
-        char* escaped_path = output_escape(chunk->items[i]->path, config->eight_bit_output);
+        char* escaped_path =
+            output_escape(file_wire_path(chunk->items[i]), config->eight_bit_output);
         if (!escaped_path) {
           chunk_destroy(chunk);
           directory_scanner_destroy(scanner);
@@ -529,7 +530,7 @@ static int send_list_only(const Config* config) {
         entries = grown;
         capacity = new_capacity;
       }
-      char* path = str_dup(f->path);
+      char* path = str_dup(file_wire_path(f));
       if (!path) {
         oom = true;
         break;