nix/doc/manual/rl-next/repl-and-logging.md

synopsis	issues	prs
Fix chopped up repl output	12599	12604

The REPL and logger now contend for standard output in a much more systematic manner. In particular, the synchronisation mechanism is more error-tolerant, by virtue of now using RAII. REPL output should no longer interrupt or be interrupted by the logger mid-message,