fix(receiver): defer --dirs directory mode to avoid EACCES on children

file_save_directory_to_disk() applied the exact source mode (fchmod)
inline for explicit --dirs/STATUS_MKDIR entries.  A restrictive source
mode (e.g. 0555) then made the directory read-only before its children
were written, so a non-root receiver failed each child with EACCES.  The
recursive -a path never hit this because it defers directory metadata.

Remove the inline fchmod and let the existing deferred
dir_metadata_list_apply() stamp the exact mode at end of transfer, as the
recursive path does.  Keep the inline ownership and xattrs (a direct
file_save_to_disk_full() caller has no deferred pass) and document the
resulting intentional ordering.  Capture errno before output_escape() in
the inline timestamp diagnostic so strerror() reports the real error, and
add the missing trailing newline to tests/test_xattr.c.

tests/test_xattr.c

@@ -603,4 +603,4 @@ void test_xattr() {
   test_fake_super_no_real_chown();
   test_fake_super_storage_resolution();
   test_file_save_directory_applies_xattrs();
-}
+}