draupnir review: the remote job dir was keyed on the basename alone, so two
local dirs with the same name shared one remote dir, and a rerun inherited
stale files. The dir is now <basename>-<8 hex of sha256(abs path)>, and it is
mirrored with rsync --delete, confined to that one directory. There is no rm on
a computed path. Verified: a file deleted locally is gone from the rerun's
remote dir. The /defaults stderr line is documented as harmless noise.