cmd_manifest emitted a null skeleton (binary_sha256: null) while the
real signed manifest existed on disk at
cog/artifacts/manifests/<arch>/manifest.json.
- New manifest module include_str!-embeds the real signed manifests
(x86_64 + arm), selected by build target arch.
- cmd_manifest parses-then-emits the embedded signed manifest, mirroring
cog-pose-estimation manifest_roundtrips. CLI now reports the real
binary_sha256, weights_sha256, Ed25519 signature, and honest
build_metadata (training_class1_accuracy = 0.343).
Failing-on-old test:
manifest::tests::embedded_manifest_has_non_null_binary_sha256 (+
embedded_manifest_is_signed, embedded_manifest_id_matches_cog).
Verified end-to-end: cog-person-count manifest -> non-null sha256.
Co-Authored-By: claude-flow <ruv@ruv.net>