Runbook: hypothesis / :killed

Assert verdict=:killed and evidence of the kill: which criterion fired, observed how. A kill is a RESULT — it retires a belief and usually implies design work (the roadmap says what dies with it: kill H1 and the core loop is wrong, not under-featured). Write the evidence so the next design argument can cite it. Judgment stage, same rules as :validated: sign reasoning a stranger could dispute.