CVE-2026-53785: create a transfer's implied parent directories and the
generator's directory entries through the symlink-race-safe parent walk, so
a symlink planted at a parent component cannot make a non-chrooted receiver
create them outside the destination tree
CVE-2026-53783: complete the els3 fix, which was partial: add --confine-root
so a restricted-directory server also refuses the names that arrive over the
protocol (file-list names, --files-from lines, filter merge files), and have
rrsync pass it; hand rsync a pinned receiver directory option and an existing
directory destination as /proc/self/fd/N/. and any other existing destination
as its pinned parent plus the leaf, so --partial-dir no longer discards
completed files and a push onto an existing file no longer fails