Contract 7.1.9

The badge tools after the Elixir Gym's fifth run on them (feedback #279-#280), and a badge stamp the players gate caught.

• A population with no profile read (players_considered 0) says its badges are unknown, not absent: an opponent seen only in battles had read as holding no badges (#279).
• A holder's observed_at is the newest profile read, from the snapshot or the poll ledger: a poll that found nothing changed leaves the day row as it was, so the stamp had lagged players_profile.meta.source_polls by a poll.

Additive.