- resubmit: updatePo distinguishes intent "resubmit" (from EDITS_REQUESTED)
from "submit" (from DRAFT); test now sends "resubmit" (makePoForm widened).
- payment: MANAGER now holds process_payment, so the "wrong permission"
negative test uses TECHNICAL (which lacks it).
- vendor: provideVendorId rejects on a missing vendorId *code*; seeded
unverified vendors carry codes, so create a genuinely code-less vendor.
Full integration suite: 108/108 passing.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>