DR-070 — Closed-task guard: every cited id is status-checked; reopens are explicit

Status: accepted · S472 (root cause: S469 “reopen an id-131 slice” on a 39/39-closed task)

No handoff prompt, DR text, deployment table, or dispatch brief may name an id-N / {N.M} as a live extension point without a status check (ledger-cli get task <id> status). A done record is not an extension point — new work routes to a new task/subtask or backlog. Reopening a closed task is permitted only as an explicit, reasoned statement (“reopen ID-N: ”), never as an implicit assumption of openness.