Replaces eighteen hand-rolled temp-directory helpers, most of which disambiguated by pid and so assumed one test process at a time. The five standing in for ~/.config/atgc are pinned to 0700: tempfile defaults a directory to 0o777 & ~umask, which would leave the mode assertions in those modules weaker than the thing they check. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>