compute_diff now emits a simple subset of jsondiff's marshaled syntax:
plain key assignment for adds and full-value changes (lists replaced
wholesale), $delete for removed object keys, and $replace only when a
dict replaces a non-dict. Removed keys are always $delete, even when the
object becomes empty (jsondiff emitted $replace: {}).
apply_diff (single implementation in serialization.base, used by both
replay and patch_state) additionally accepts jsondiff-produced patches:
positional $insert/$delete and per-index nested diffs on lists, plus
$ escaping of user keys and values per the marshal format.
jsondiff moves to the dev dependency group; it is used only by tests
that verify patch compatibility in both directions.
LeoVasanko