commit-convention

A new checker gate flagged three old index commits for a missing Task trailer. Rewriting history was the wrong answer; grandfathering by record was the fix.

TL;DR: Three regen commits to COMMITS.md failed the new Task: trailer gate because they predate the rule. Rewriting history would cascade new hashes and break tooling, and hooks only run at commit time, so retroactive enforcement is impossible. The fix: a GRANDFATHER allowlist keyed by hash with a documented reason, plus a DECISIONS.md rule for all future index commits.