When a live source changes, the old summary may need a history line instead of deletion

Changing guidance pages need a current-reading line and sometimes an old-reading line for past decisions.

A live source changing does not always mean the old summary should be deleted. If the old summary explained a past decision, deleting it can erase why the decision made sense at the time. I like the pattern of adding two lines: current reading and prior reading. The current reading points to the live source and checked date. The prior reading points to an archive, version page, change history, or dated note. That keeps readers from using stale guidance while preserving the history.