Development record

The brief at .abcd/development/brief/04-surfaces/11-history.md:255-256 mentions `abcd history discard` only as the confirmed discard of a quarantined file, and describes `staged` only as per-repo or all-repos. The shipped `history discard <staged-filename> --yes` deletes a staged or a quarantined raw transcript, and both `discard` and `staged` take --root-sha to reach a repository whose checkout is gone (commands/history.md:73-77, 190-236).