Improve AI disclosure beyond Schema.org comment field

## Summary

JSON-LD files under `data/objects/summoned` currently disclose AI-generated metadata with a Schema.org `comment` (for example in earthface files):

"comment": "This dataset metadata was generated with the use of AI and reviewed by an expert. If you see any mistakes please file an issue on GitHub at https://github.com/earthcube/communityCollections/issues."

This works as a short-term disclosure, but Schema.org does not yet have a clear, dedicated way to declare that generative AI was used. See:

- https://github.com/schemaorg/schemaorg/issues/3391

We also need a structured signal that search and display UIs can detect reliably, so AI-assisted records can show an icon, keyword tag, or banner when queried and rendered.

## Direction

1. Keep the human-readable `comment` field as our current AI disclosure text.
2. Track Schema.org issue [#3391](https://github.com/schemaorg/schemaorg/issues/3391) until Schema.org defines recommended markup for generative AI use.
3. Adopt a machine-readable AI-disclosure field (Schema.org-recommended when available; interim structured field if needed) so consumers can detect AI-assisted metadata and show an icon, keyword tag, or banner in query results and detail views.
4. Apply that pattern across JSON-LD under `data/objects/summoned`.
5. Update `scripts/generate_jsonld.py` so newly generated files include both the human-readable disclosure and the machine-readable signal.

## Scope

- Files under `data/objects/summoned`
- Generator logic in `scripts/generate_jsonld.py`
- Downstream display of AI disclosure (icon / keyword tag / banner)

## Acceptance criteria

- [ ] Keep `comment` as the human-readable disclosure
- [ ] Add or adopt a machine-readable AI disclosure signal usable by UIs
- [ ] Track Schema.org #3391 and migrate to the recommended markup when available
- [ ] Apply the pattern to JSON-LD under `data/objects/summoned`
- [ ] Update the generator so new files match
- [ ] Confirm queried/displayed results can show an AI icon, keyword tag, or banner from that signal