A reader dates a book by the book. An inline 截至 <date> or （核验日期：<date>）
tells them nothing they cannot infer, and it decays: this cluster's clearest
case is the eight files that carried 截至 2026-05-18 while git showed they were
written 33 days earlier, one commit having later nudged the date a day for
visual consistency.
Two kinds of date deliberately survive, because they are not as-of stamps:
- Forward-looking deadlines. "Sonnet 5 的 $2/$10 是截至 2026-08-31 的介绍价"
states when a price expires; deleting that date would lose a fact.
- Ledger metadata. verified_at / expires_at / ttl_days in the volatile-facts
appendices are inputs to check_volatile_facts(), which fails the build when
they lapse. That is the right home for a verification date — machine-checked
and self-expiring, rather than prose nothing re-earns.
Event dates are untouched throughout (2026-06-09 GA, 2026-06-12 暂停). Where a
sentence needed the sequence, "截至 2026-07-09 官方模型页已恢复" became
"官方模型页此后已恢复", which keeps the ordering without the observation date.
yeasy