833a0432b8
Review round 3 fixes: - write_all helper: handle partial writes from signals - EPIPE on write side: catch BrokenPipeError (child dead), not all OSError - Read-side OSError: diagnose on stderr + exit 1 (not silent truncation) - parse_netstring: sanity cap 1<<24, return content only (not tuple) - 128+WTERMSIG for signal-killed children (shell convention) - 24/24 pytest green