Round 2 per Sage's notes revs 521 and 523: a repeated Host is 400 before
any check; HEADER with a Host other than NAME is 403 proxy Host refused;
HEAD, x.NAME and --auth-header tests; the README proxy contract lines.
Candidate manifest 17b6d7f6, base 17ea0dbc. 34 of 34 mutants killed;
gate green.
Co-Authored-By: Claude Opus 5.5 <[email protected]>
jason.woltjeandClaude Opus 5.5