internationalized-array: defaultLanguages patches on mount, so opening a form persists an empty draft

[joaodotwork]

Describe the bug

With defaultLanguages configured, opening a new-document form is enough to persist a draft,
even if the editor types nothing and navigates away.

The plugin applies its defaults from an effect that patches the document on mount. In Sanity a
patch is what brings a draft into existence, so the act of rendering the form creates one. The
resulting document contains only the seeded identity rows — note there is no value key anywhere:

{
  "_id": "drafts.X6w3bu3dUaiAMZ8jI4zmao",
  "_type": "project",
  "title":       [{ "_key": "en", "_type": "internationalizedArrayStringValue",             "language": "en" }],
  "description": [{ "_key": "en", "_type": "internationalizedArraySimplePortableTextValue", "language": "en" }]
}

In our Studio these accumulate as "Untitled" documents, because the desk lands on a
new-document form on its own after you delete or unpublish something — so an editor doing routine
cleanup leaves a draft behind each time without ever choosing to create one. We had collected ten
before noticing.

The cost is not only clutter. These drafts are untitled, image-less and untagged, so any
dataset-wide quality query counts them: they were being reported as documents missing a
description, missing images, missing every taxonomy field, and so on — a content-completeness
signal reading them as real work in progress.

To Reproduce

internationalizedArray({
  languages: [
    { id: 'en', title: 'English' },
    { id: 'pt', title: 'Portuguese' },
  ],
  defaultLanguages: ['en'],
  fieldTypes: ['string', 'text'],
})

1. Open any document type with an internationalized field via Create new.
2. Type nothing. Navigate away.
3. Query the dataset with the raw perspective:
   *[_id in path("drafts.**")] — a new draft is there, holding only the seeded rows.

Watching the network while the form mounts shows the /data/mutate/ request that creates it.

Expected behavior

Rendering a form should not write. The seeded language rows are a presentation default — somewhere
to type — so ideally they would exist in the form value without being patched to the document until
the editor actually enters content.

Which versions of Sanity are you using?

• sanity-plugin-internationalized-array 5.1.3
• sanity 6.8.0

Workaround

Removing defaultLanguages stops it: with no defaults to apply, the effect makes no patch and no
draft appears until the editor types. Confirmed by driving the create form in a browser and counting
drafts either side — zero /data/mutate/ requests afterwards.

The cost is that localized fields no longer start with a row to type into. buttonLocations
defaults to ['field'], which puts an Add button on every localized field; adding 'document'
gives a single document-level control instead, which keeps it to one deliberate click per document.
That combination has been a reasonable trade for us, but it is a trade rather than a fix.

Possibly related

#527 reports a different symptom of what may be the same mechanism — defaultLanguages rows
becoming non-removable, blocking publish when a required sub-field is empty. Both come down to the
plugin enforcing its defaults against the stored document rather than the form state, so a change
there might address both. Filing separately since the observable problem is different.