Development record

The brief at .abcd/development/brief/04-surfaces/27-implement.md:59-61 says that outside a checkout, or in a repository with no commit, every implement sub-verb refuses and nothing is created. `abcd implement load --site preflight` runs and exits 0 outside a checkout: internal/surface/cli/implement_load.go:148-152 resolves the checkout root only optionally, and the load help documents a machine check with no checkout precondition.