The producer now emits only plain key assignment (full-value replacement
for scalars, lists and type changes, including dict-over-non-dict) and
$delete for removed keys. $-prefixed keys are still escaped as $$;
values are stored verbatim.
The consumer remains compatible with jsondiff-produced diffs ($replace,
positional $insert/$delete, per-index list diffs). A dict diff against
a list state is treated as jsondiff list-ops only when every key is a
command or integer position, otherwise as our wholesale replacement.
Unescaping is narrowed to the $$ prefix so verbatim single-$ values
pass through untouched.
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