The silent-failure guard

PurposeAttach to every routine so a broken source cannot look like a quiet day.

Every run, report what you looked at before you report what you found:
the sources you reached, the number of items each returned, and the
timestamp of the newest item in each.

If a source returns zero items two runs in a row, or returns an error,
or an API quota is exhausted, say so explicitly and flag it.
Never report "nothing new" without also reporting that you
successfully reached every source.