cloneDataFromOriginalDoc mangles json array-of-arrays into index-keyed objects on partial update

Describe the Bug

On a partial payload.update / REST PATCH that omits a json field, cloneDataFromOriginalDoc (dist/fields/hooks/beforeChange/cloneDataFromOriginalDoc.js) shallow-clones each array row with {...row}. When the stored value is an array of arrays (e.g. [[lng, lat], ...] coordinate tuples), every inner array is spread into an index-keyed object {"0": lng, "1": lat}.

On a publish operation this trips the field's validate, but draft saves skip validation, so the corrupted shape persists to the database. Downstream consumers that iterate the tuples then crash with TypeError: object is not iterable.

Link to the code that reproduces this issue

n/a (minimal repro below)

Reproduction Steps

1. Define a collection with a json field, drafts enabled.
2. Save a document whose json value is an array of arrays, e.g. [[1, 2], [3, 4]].
3. Run a partial update that omits the json field:

   await payload.update({
     collection: 'things',
     id,
     data: { someOtherField: 'x' }, // json field NOT included
     draft: true,
   })
   

4. Read the stored value — it is now [{ "0": 1, "1": 2 }, { "0": 3, "1": 4 }] instead of [[1, 2], [3, 4]].

Element order is preserved (so it is recoverable), but the nested arrays are gone.

Expected

Nested arrays inside a json value should be preserved verbatim when the field is omitted from a partial update. A shallow {...row} clone should not be applied to array rows — a structured/deep clone would retain the original shape.

Environment

• Payload: 3.85.1
• Database: @payloadcms/db-postgres (json column)

Start in dist/fields/hooks/beforeChange/cloneDataFromOriginalDoc.js and reproduce the partial payload.update or REST PATCH that omits the json field. Verify that array-of-arrays values retain their nested array shape after draft saves, and add regression coverage for the [[1, 2], [3, 4]] example so the stored value is unchanged.