Adds a defense-in-depth audit row to impersonationAuditLogs when the
staff-side owner-bypass path fires. Mirrors the failure-isolation
pattern in src/middleware/portalAudit.ts: insert failures are logged
and swallowed so a working read can never turn into a 500.
- New writeOwnerBypassAudit helper called only when isOwner === true.
- No DB migration; petId + actorStaffId go inside metadata jsonb.
- resolveImpersonationClientId stays pure (no audit side effects).
- Positive + negative tests + a cross-tenant regression test.
- UAT_PLAYBOOK.md §3.19d: TC-API-3.19d documents the audit assertion.
Parent tracking: GRO-2062 (Paperclip).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>