Development record

The lab chapter says the matrix plan is built from the declaration and the machine's configuration alone (.abcd/development/brief/04-surfaces/31-lab.md:34), and `abcd lab matrix --help` enumerates its exit 2 refusals. The verb also refuses, exit 2, a lab with no passing preflight (internal/core/lab/procedure.go:58-60, reached from internal/core/matrix/consent.go:126). Neither text names that refusal.