itd-91 has every commit trailer follow the project's chosen AI-credit convention; the announce brief requires an announcement's Assisted-by to be abcd's own label and nothing else

itd-91 has every commit trailer follow the project's chosen AI-credit convention; the announce brief requires an announcement's Assisted-by to be abcd's own label and nothing else

A premise contradiction (severity minor) found by the cross-document consistency pass.

• End A: .abcd/development/intents/drafts/itd-91-ai-attribution-preference.md:17 — "Your answer is recorded once, in the repo, and from then on every commit trailer, pull-request body, and generated record uses exactly that convention."
• End B: .abcd/development/brief/04-surfaces/38-announce.md:84 — "its Assisted-by abcd's own abcd:<version> label and no other value"

itd-91 records a per-project choice of convention, from none to Co-Authored-By: to custom wording, and says every commit trailer, pull-request body and generated record then uses exactly that convention. The announce chapter checks every announcement against a validator that requires its Assisted-by trailer to be abcd's own abcd:<version> label and no other value. In a project that chose a different convention, announcement commits either fail the validator or ignore the project's choice.

Evidence: .abcd/work/reviews/2026-10-26-consistency/00-summary.md, finding 737.