The box-drawing character filter was dropping ANY line containing │ or ─,
including dsd-fme data lines that use these as column separators (e.g.
"DMR BS │ Slot 1 │ TG: 12345 │ SRC: 67890"). Now only filters lines
that are purely decorative (no alphanumeric content).
Also adds -J /dev/stderr so dsd-fme writes its event log to stderr
where we capture it, and debug logging of raw stderr lines.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>