Shared _sanitize_ctl (unconditional, nc-document) and _sanitize_ctl_tty
(strips only when stdout is a terminal) now live in cygwin-safe.sh. nc-msgs,
nc-parse, and the hl7-* tools route stdout through the tty-gated variant, so a
terminal is protected from raw HL7/NetConfig control bytes while pipes and
redirects stay byte-exact (the 0x1c framing route_test needs is preserved).
Exit codes propagate via PIPESTATUS. ssh-helper _read_hidden installs its
restore trap before stty -echo on every path and saves/restores the prior trap.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>