fix(fs): rsync push iconv direction; gate empty-dir emission; reclassify --temp-dir

- --iconv now matches rsync's push direction: the destination charset is the
  client spec's REMOTE half, so a default receiver writes wire names verbatim;
  a server's own --iconv LOCAL overrides it (daemon charset analog). Updated
  unit + integration tests and added a default-server differential gate case.
- Empty-directory emission is gated behind a new ScannerOptions.emit_empty_dirs
  set only by the real sender, so low-level scanner helpers keep the historical
  file-only list.
- --temp-dir reclassified to Divergent: relative dirs match rsync exactly
  (resolved under the destination), but an absolute path is deliberately
  rejected by the confined receiver; differential test added.
- Docs/tally: 109 Parity / 22 Caveat / 25 Divergent.

src/client/client_send.c

@@ -412,6 +412,9 @@ static bool prepare_scanner(const Config* config, int num_threads, PreparedScann
   options->exclude_per_dir_filter_files = config->per_dir_filter_count >= 2;
   options->dirs = config->dirs;
   options->relative = config->relative;
+  /* A real recursive transfer recreates empty source directories (rsync
+     parity); low-level scanner users leave this off. */
+  options->emit_empty_dirs = true;
   /* --no-implied-dirs only has meaning with -R (rsync): without it the option
      is a documented no-op, so the scanner must not suppress directory
      metadata. */

src/client/scanner.c

@@ -1399,8 +1399,9 @@ Chunk* directory_scanner_next(DirectoryScanner* scanner) {
     if (entry == NULL) {
       /* The directory is exhausted: if nothing was transferred or descended
          from it, recreate it at the destination as an explicit entry. */
-      if (!scanner->current_dir_produced && !scanner->options.prune_empty_dirs &&
-          !scanner->options.list_dirs && scanner->options.file_list == NULL) {
+      if (scanner->options.emit_empty_dirs && !scanner->current_dir_produced &&
+          !scanner->options.prune_empty_dirs && !scanner->options.list_dirs &&
+          scanner->options.file_list == NULL) {
         if (!scanner_emit_empty_dir(scanner, chunk_data))
           scanner->failed = true;
       }

src/client/scanner.h

@@ -151,6 +151,12 @@ typedef struct {
   bool capture_dir_times;
   ArrayList* dir_entries;
   mtx_t* dir_entries_mutex;
+  /* Recreate empty source directories on a recursive transfer: emit a
+   * payload-less directory entry for every traversed directory that produced
+   * no transferred/descended child.  Off by default so low-level scanner users
+   * (unit helpers, --list-only) see only the historical file list; the real
+   * sender sets it in prepare_scanner. */
+  bool emit_empty_dirs;
   /* --no-implied-dirs with -R + --files-from: a directory that is only an
    * implied parent of a listed entry (not itself listed, nor below a listed
    * directory) must not carry source metadata; it is created with default

src/client/usage.c

@@ -90,8 +90,8 @@ void print_usage(void) {
   printf("                      entry's destination mirror receiver-side.  Independent of\n");
   printf("                      --delete (it does not imply --delete; a non-empty directory\n");
   printf("                      mirror is removed only with --force or --delete)\n");
-  printf("  -m, --prune-empty-dirs  Do not transfer empty directory entries (--dirs mode);\n");
-  printf("                      recursive transfers never send empty dirs\n");
+  printf("  -m, --prune-empty-dirs  Do not create empty directories (a recursive transfer\n");
+  printf("                      otherwise recreates them, like rsync)\n");
   printf("  Note: each timing flag implies --delete.  Combining a timing flag with\n");
   printf("  --no-delete (in either order) is rejected as a config error.\n");
   printf("  --ignore-existing  Skip files that already exist on receiver\n");