Push builds have been RED on the lint step since ~build 209 from accumulated
formatting drift. This is the mechanical cleanup: ruff format + ruff --fix
(UP038 isinstance unions, SIM105 contextlib.suppress, UP031 f-strings, SIM115
tempfile context manager), shfmt -i 2 -ci, nixpkgs-fmt/statix/deadnix (merged
attrsets, dropped unused lib args), yamllint, and shell quoting fixes in
tests/lasuite-docs/setup_custom_tests.sh. No behaviour changes intended;
lint: PASS, unit tests: 138 passed.
Root cause of the 2 failing custom tests: TLS_FLAVOR=notls → dovecot refuses plaintext auth over
network 143, so host-side IMAP login/auth isn't a meaningful signal. Smoke2 PROVED the in-container
path: sendmail (postfix container) local-injects a marker mail → doveadm search (imap container) finds
it in INBOX. test_mail_flow now exercises the real postfix→rspamd→dovecot deliver/store/fetch via
exec_in_app(service=smtp/imap). Dropped test_imap_login (network plaintext-auth disallowed under notls).
test_mailbox (create+config-export read-back) unchanged. PARITY.md updated.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>