Builds claw from the current HEAD, then checks that the binary's
git_sha matches git rev-parse --short HEAD. Exits non-zero if the
binary is stale or provenance is opaque (git_sha: null).
Usage:
CLAW=$(bash scripts/dogfood-build.sh) # fail-fast if stale
$CLAW version --output-format json # provenance confirmed
Addresses ROADMAP #69: dogfooders using a stale installed binary
cannot attribute behavior to specific commits. This script makes
dogfood round zero unambiguous.
Also documents the safe workaround for contributors who have a
stale system-installed binary.
