remake: earlier epochs' metadata carried as built, not as it stands

Review 4, F6: a snapshot judged which earlier epochs' metadata to leave out as the base
epoch's snapshot built it (1254), but copied `_continuum/epochs` from the base as it
stood. In a swarm without a policy, a member's rewrite of an entry (its window, kind,
clock, translation) went into the next epoch, and was "as built" there; an entry it
added was carried and never left out, one it removed not carried.

Now `_continuum/epochs` is copied from the base epoch's snapshot change too
(`as_built`), then pruned; the first epoch's base carries none. The test adds a
generation and narrows a window after the snapshot: neither reaches the next one.

0 files changed, 0 insertions, 0 deletions