All SQLite work in the package serializes on one allocator lock under
-race, so its run time follows the total work. Tests that need one
backup to a file:// destination now copy a shared backup made once.
The sweeper and locality fixtures are smaller, and the list truncation
test encodes one manifest instead of 1001, which cut the part of the
run that is not parallel from about 11 to 3 seconds.
Model: opus-5-5
sneak