feat(subscribers): raise the follow-list cap to 10,000, and report it master
2000 was `listRecords`' generic backstop, inherited from when the popup walked the list inline; it binds on the reader rather than on a publication, so a reader following more than that could be told they do not follow an account they followed early. `listRecords` now takes a limit, and the follow walk asks for 10,000 — a hundred requests, once a day, in the worker. The number is set by how long an MV3 worker can be relied on to live, not by politeness to the PDS: a walk killed mid-flight caches nothing. Going further wants a walk that resumes from a cursor rather than a bigger constant. `followingDids` also reports stopping at the cap, which was the part nothing recorded. Past it the set is a prefix, so absence from it is not a "no" — the owner card's line already draws nothing on a miss, and the subscriber row now says which of the two caps could be hiding a face.